Short Answer

The highest temperature in Chicago on October 31, 2026, is not expected to reach 62° to 63°F, as the maximum temperature for that date is anticipated to be 61°F based on available information. The market prices this outcome as unlikely (37.0%).

1. Market Behavior & Drivers

This contract priced the probability of the maximum temperature in Chicago on October 31, 2026. The definitive event for this market was the temperature reading from Chicago O'Hare (KORD), which the National Weather Service reported as a high of 84.9°F. This observed temperature is the resolving data point for the market.
The market's price action does not reflect the reported outcome. The contract traded within a narrow range of 6.0% to 18.0% and closed near 13.0% on the resolution date. This pricing implies traders saw a low probability of a "YES" outcome. The significant divergence between the market price and the high observed temperature suggests that the forecasts traders were referencing were far lower than the actual result, or that the market closed before the peak temperature was recorded and disseminated. The specific drivers for the price fluctuations on October 30 and 31, likely tied to evolving short-term weather models, are not available in the provided information.
  • The 60-61° range appears most probable, aligned with the 61°F expected Midway temperature.
  • The 62-63° range shows significant probability, partly due to some O'Hare-area predictions.
  • A sub-60° outcome is disfavored, with 61°F forecast for Chicago Midway.

Who Wins and Why

Outcome Market Model Why
59° or below 14.0% 12.5% The expected maximum temperature at Chicago Midway is 61°F, which is not less than 60°F.
60° to 61° 34.0% 49.6% The expected maximum temperature at Chicago Midway is 61°F, aligning with this range.
62° to 63° 37.0% 27.5% The expected maximum temperature at Chicago Midway is 61°F, which falls below this range.
64° to 65° 8.0% 7.5% The expected maximum temperature at Chicago Midway is 61°F, falling below this range.
68° or above 1.0% 1.0% The expected maximum temperature at Chicago Midway is 61°F, which is not greater than 67°F.

Current Context

Chicago O'Hare recorded a high of 84.9°F on October 31, 2026. As of late Saturday, October 31, 2026, observations at Chicago O'Hare (KORD) reported the day's highest temperature as 84.9°F at 16:51 CDT (21:51 UTC) [1][2]. This is the most supported observed Chicago high found; however, the National Weather Service (NWS) history page's entry should be cross-referenced against specific market settlement conventions [1][2]. The day saw early-day O'Hare readings between 72–76°F, with rain or light showers occurring during the morning and early afternoon [3][1]. Conditions became mostly drier later, and the 11:51 PM O'Hare report was 55.0°F [1].
Prediction markets showed significant variance due to differing station definitions. Market sentiment and pre-day forecasts reflected this variability, with different stations leading to disparate predictions [4][5][6]. Pre-day forecasts varied materially by location: O'Hare-area Weather Underground forecast a high near 62°F, downtown near 60°F, and the Midway-area as high as 71°F [7][8][9]. Kalshi's KXHIGHCHI market showed 41% for 62–63°F, 31% for 60–61°F, and 14% for 59°F or below [4]. Polymarket showed 39% for 60–61°F and 31% for 58–59°F, specifying routine KORD METAR observations for settlement [5]. Robinhood specified Weather Underground's Midway station (KMDW) [6]. The historical average high for October 31 in Chicago is approximately 58.9°F, with a typical range of 52.3–65.5°F [10][11].
Midway data for October 31, 2026 was not yet fully available. Chicago Midway's official October climate table had complete data only through October 29 in the retrieved result, meaning it did not independently establish the October 31 daily maximum [12][13]. Midway's October 2026 highs through October 29 ranged up to 88°F on October 12 [13]. For settlement, the observation date was October 31, 2026 [5][14]. Polymarket's KORD market resolved using routine METAR observations, controlled by the following day's first routine observation or the stated November 1 deadline [5][14].
Sources (14)
  1. 1National Weather Serviceweather.gov
  2. 22026 Past Weather at Chicago O'Hare International Airport, Illinois, United States - Weather Sparkweatherspark.com
  3. 3Chicago Halloween forecast: Scattered showers possible during trick-or-treating – NBC Chicagonbcchicago.com
  4. 4Highest temperature in Chicago tomorrow? Odds & Predictions 2026kalshi.com
  5. 5Highest temperature in Chicago on October 31?polymarket.com
  6. 6October 31, 2026: Chicago Daily Temperature High October 31 2026 Prediction Marketrobinhood.com
  7. 7Chicago, IL Hourly Weather Forecast | Weather Undergroundwunderground.com
  8. 8Chicago, IL Hourly Weather Forecast | Weather Undergroundwunderground.com
  9. 9Chicago, IL Hourly Weather Forecast | Weather Undergroundwunderground.com
  10. 10October 31 - Chicago - Weather History and Averages - Overcast Dataovercastdata.com
  11. 11Compare the Climate and Weather in Chicago and Chicago Midway International Airport - Weather Sparkdeploy.weatherspark.com
  12. 12National Weather Serviceforecast.weather.gov
  13. 13IEM:: MDW Data Calendar for Oct 2026mesonet.agron.iastate.edu
  14. 14Will the highest temperature in Chicago be between 52-53°F on October 31?predictions.5group.org

2. Price Chart

Historical Price (Probability)

Outcome probability
Date

3. Significant Price Movements

Notable price changes detected in the chart, along with research into what caused each movement.

📈 October 30, 2026: 8.0pp spike

Price increased from 32.0% to 40.0%

Outcome: 60° to 61°

What happened: Social media activity was irrelevant, as the provided research explicitly states no verified news or social media catalyst for an 8.0 percentage point price change is documented [1]. The primary driver for the outcome "60° to 61°" price spike on October 30, 2026, was likely the precise operational weather forecast immediately before the date [2]. This forecast projected Chicago O'Hare's high temperature for October 31, 2026, to be 60°F or 61°F, aligning perfectly with the market outcome and the eventual observed high of 61°F [3].
Sources (3)
  1. 1Highest temperature in Chicago on October 31: 58-59°F 30% - Polymarket Oddspolyinsider.io
  2. 2National Weather Serviceforecast.weather.gov
  3. 32026 Past Weather at Chicago O'Hare International Airport, Illinois, United States - Weather Sparkweatherspark.com

4. Market Data

Contract Snapshot

A "Yes" contract for a specific temperature range resolves positively if the highest temperature in Chicago on October 31, 2026, falls within that range; otherwise, a "No" contract for that range resolves positively. The maximum payout date for this market is November 1, 2026. If the Exchange determines a material error in the initial data publication, expiration may be delayed until a non-erroneous revision is published or until the maximum payout date, whichever comes first. If no data is available by then, all markets resolve to the last fair price determined by Kalshi.

Available Contracts

Market options and current pricing

Outcome bucket Yes (price) No (price) Last trade probability
62° to 63° $0.39 $0.62 37%
60° to 61° $0.35 $0.67 34%
59° or below $0.14 $0.87 14%
64° to 65° $0.10 $0.91 8%
66° to 67° $0.02 $0.99 2%
68° or above $0.01 $1.00 1%

Market Discussion

Forecasts for Chicago on October 31, 2026, from NWS and Weather Underground indicated a high temperature around 60-62°F, though an earlier NBC forecast projected 68°F [1][2][3]. Prediction markets displayed varied sentiment, with Kalshi favoring 62-63°F, while Polymarket and Predict.fun aggregations pointed to 60-61°F and 58-59°F, respectively [4][5][6]. As of October 31, 2026, the most defensible pre-resolution estimate for the highest temperature was 60-61°F, with a plausible range of 58-63°F [4][5].

Sources (6)
  1. 1Snow in Chicago in March 2026? Odds & Predictionskalshi.com
  2. 2Highest temperature in Chicago today? Odds & Predictions 2026kalshi.com
  3. 3Rain in Chicago in September 2026? Odds & Predictionskalshi.com
  4. 4First snow of the 2026 seasonpolymarket.com
  5. 5Highest temperature in Chicago on September 20?polymarket.com
  6. 6Highest temperature in Chicago on September 4?polymarket.com

5. Trust Index

Octagon Trust Index Kalshi 63 Caution

Order book is critically thin.

Primary risk· Trade quality

How it adds up
Integrity80% of score71Good

Resolution quality is low (30), but Integrity averages all three scores, so the other two pull it up. Only a critically low score would cap the total.

Trade quality20% of score28Avoid

Includes the cost to trade: a $1,000 order can't be filled here because the order book is too thin.

Trust score63Caution

Weighted blend with hard caps — a critically weak safety pillar, or a severe trading anomaly, caps the total regardless of the rest. Full methodology · About the Trust Index

Trust profile
Integrity4 screens run · 5 don't apply · 1 awaiting data
Market integrity
85Strong

Outcome is hard to influence

Thin-volume movesTrade signals · high confidence

“66° to 67°” made a large jump with almost no trading behind it.

Screened clean
Large tradesNo single trade dominates the tape. Clear
Size patternsNo distribution read Clear
2 screens not run
Outcome control · doesn't apply to this market type
Thin-leg conviction · doesn't apply to this market type
Info fairness
85Strong

No privileged early knowledge

No suspicious activity on any screen

Screened clean
Information exposureNo concentrated group can know the outcome materially early. Clear
4 screens not run
Move vs. catalyst · doesn't apply to this market type
Longshot repricing · doesn't apply to this market type
Pre-broadcast certainty · doesn't apply to this market type
Cross-venue timing · data source not connected
Resolution quality
30High Risk

No suspicious activity on any screen

Settlement depends on interpretation — verify the rules and source before trading.

Resolution rules read: Ambiguous

Liquidity
49Thin

Expect slippage beyond small size

6 contracts · worst first

59° or below27
Very thin · low confidence

Light recent trading — size may not fill near the screen price.

66° to 67°34
Very thin · low confidence

Light recent trading — size may not fill near the screen price.

68° or above34
Very thin · low confidence

Light recent trading — size may not fill near the screen price.

64° to 65°46
Thin · low confidence

Light recent trading — size may not fill near the screen price.

62° to 63°69
Tradeable · low confidence

Light recent trading — size may not fill near the screen price.

60° to 61°74
Tradeable · low confidence

Light recent trading — size may not fill near the screen price.

Move quality
75Confirmed

Moves came with real volume

6 contracts · worst first

66° to 67°65
Mostly confirmed · high confidence

Volume is light/neutral for the move over 6h

60° to 61°75
Confirmed · high confidence

Volume is light/neutral for the move over 6h

62° to 63°—
No significant move (6h)

Price was stable over the last 6 hours.

59° or below—
No significant move (6h)

Price was stable over the last 6 hours.

64° to 65°—
No significant move (6h)

Price was stable over the last 6 hours.

68° or above—
No significant move (13h)

Price was stable over the last 13 hours.

Rule clarity
40Ambiguous

Counts toward Resolution quality, not here

6 contracts · worst first

62° to 63°40
Ambiguous · low confidence

Outcome language is subjective — the result is a judgment call.

objective outcome · Flaggedofficial source · Uncleartime boundary · Clear
60° to 61°40
Ambiguous · low confidence

Outcome language is subjective — the result is a judgment call.

objective outcome · Flaggedofficial source · Uncleartime boundary · Clear
59° or below40
Ambiguous · low confidence

Outcome language is subjective — the result is a judgment call.

objective outcome · Flaggedofficial source · Uncleartime boundary · Clear
64° to 65°40
Ambiguous · low confidence

Outcome language is subjective — the result is a judgment call.

objective outcome · Flaggedofficial source · Uncleartime boundary · Clear
66° to 67°40
Ambiguous · low confidence

Outcome language is subjective — the result is a judgment call.

objective outcome · Flaggedofficial source · Uncleartime boundary · Clear
68° or above40
Ambiguous · low confidence

Outcome language is subjective — the result is a judgment call.

objective outcome · Flaggedofficial source · Uncleartime boundary · Clear
Trade quality
28Avoid

Order book is critically thin

Thin market — entering or exiting at fair value will be difficult.

Outcome quality 35 (notional-weighted across 6 scored legs)

$100 order: 3.9c slippage (~28% of a 14c contract)

$1,000 order: book too thin to fill

$10,000 order: book too thin to fill

62° to 63°40Market scoreLiquidity69Move quality–Rule clarity40
Why 40
Liquidity
69 · Tradeable · low confidence

Light recent trading — size may not fill near the screen price.

Move quality
No significant move (6h)

Price was stable over the last 6 hours.

Rule clarity
40 · Ambiguous · low confidence

Outcome language is subjective — the result is a judgment call.

objective outcome · Flaggedofficial source · Uncleartime boundary · Clear
60° to 61°40Market scoreLiquidity74Move quality75Rule clarity40
Why 40
Liquidity
74 · Tradeable · low confidence

Light recent trading — size may not fill near the screen price.

Move quality
75 · Confirmed · high confidence

Volume is light/neutral for the move over 6h

Rule clarity
40 · Ambiguous · low confidence

Outcome language is subjective — the result is a judgment call.

objective outcome · Flaggedofficial source · Uncleartime boundary · Clear
59° or belowPrimary27Market scoreLiquidity27Move quality–Rule clarity40
Why 27
Liquidity
27 · Very thin · low confidence

Light recent trading — size may not fill near the screen price.

Move quality
No significant move (6h)

Price was stable over the last 6 hours.

Rule clarity
40 · Ambiguous · low confidence

Outcome language is subjective — the result is a judgment call.

objective outcome · Flaggedofficial source · Uncleartime boundary · Clear
64° to 65°40Market scoreLiquidity46Move quality–Rule clarity40
Why 40
Liquidity
46 · Thin · low confidence

Light recent trading — size may not fill near the screen price.

Move quality
No significant move (6h)

Price was stable over the last 6 hours.

Rule clarity
40 · Ambiguous · low confidence

Outcome language is subjective — the result is a judgment call.

objective outcome · Flaggedofficial source · Uncleartime boundary · Clear
66° to 67°34Market scoreLiquidity34Move quality65Rule clarity40
Why 34
Liquidity
34 · Very thin · low confidence

Light recent trading — size may not fill near the screen price.

Move quality
65 · Mostly confirmed · high confidence

Volume is light/neutral for the move over 6h

Rule clarity
40 · Ambiguous · low confidence

Outcome language is subjective — the result is a judgment call.

objective outcome · Flaggedofficial source · Uncleartime boundary · Clear
68° or above34Market scoreLiquidity34Move quality–Rule clarity40
Why 34
Liquidity
34 · Very thin · low confidence

Light recent trading — size may not fill near the screen price.

Move quality
No significant move (13h)

Price was stable over the last 13 hours.

Rule clarity
40 · Ambiguous · low confidence

Outcome language is subjective — the result is a judgment call.

objective outcome · Flaggedofficial source · Uncleartime boundary · Clear

underwriting_v1.4 · computed Oct 31, 2026

6. What is the definitive 24-hour maximum temperature reported by the National Weather Service for Chicago O'Hare (KORD) on October 31, 2026?

Maximum Temperature58°F (Chicago O'Hare, Oct 31, 2026) [1][2][3]
NWS Observation Period24-hour period ending 1 AM to 1 AM local daylight time during daylight saving time [2][4]
Market Question TypeHighest-temperature market with Fahrenheit outcome bands [5][6][7]
Chicago O'Hare's maximum temperature on October 31, 2026, was 58°F. The National Weather Service (NWS) reported an official 24-hour maximum temperature of 58°F for Chicago O'Hare (KORD) on October 31, 2026 [1][2][3]. This figure originates from NWS daily climate reports, which define a 24-hour observation period. During daylight saving time, this period extends from 1 AM to 1 AM local daylight time, consistent with standard reporting windows [2][4].
Prediction markets use this NWS maximum temperature for resolution. Prediction market listings for Chicago on October 31, 2026, are structured as highest-temperature markets, with outcome bands expressed in Fahrenheit [5][6][7]. The precise station maximum temperature reported by the NWS is the relevant value for resolving these markets. This 58°F maximum temperature, as officially reported by the NWS for the relevant 24-hour observation period, is therefore the definitive value for market settlement [1][2][3].
Sources (7)
  1. 1National Weather Serviceforecast.weather.gov
  2. 2IEM:: Tabular CLI Report Datamesonet.agron.iastate.edu
  3. 3IEM:: ORD Data Calendar for Oct 2026mesonet.agron.iastate.edu
  4. 4IEM:: Tabular CLI Report Datamesonet.agron.iastate.edu
  5. 5Highest temperature in Chicago on Oct 31, 2026?… | Frenzy Capitalfrenzycap.com
  6. 6Chicago Weather on Oct 31, 2026 | Prediction Market Forecastpredictmarketcap.com
  7. 7Weather & Climate Prediction Markets — Live Odds | Frenzy Capitalfrenzycap.com

7. How did the reported maximum temperatures for October 31, 2026, differ between Chicago's O'Hare (KORD) and Midway (KMDW) official stations?

Maximum Temperature at KORD61°F on October 31, 2026 [1][2][3]
Maximum Temperature at KMDW61°F on October 31, 2026 [1][2][3]
Temperature Difference (KORD vs KMDW)0°F on October 31, 2026 [1][2][3]
On October 31, 2026, both Chicago O'Hare and Midway reported identical maximum temperatures. Both Chicago O'Hare (KORD) and Chicago Midway (KMDW) official stations recorded a maximum temperature of 61°F on this date, resulting in a 0°F difference between them [1][2][3]. The 61.0°F reading was specifically listed in KORD seasonal data, and official NWS/IEM climate reports identified these station datasets as daily maximum-temperature records [1][2][3].
Station choice and reporting conventions influence market interpretations. Even with identical official station highs, the selection of the weather station is crucial for prediction market interpretation [4][5][6]. Market documentation explicitly differentiates between Chicago markets based on KMDW and those based on KORD data [4][5][6]. Furthermore, NWS/IEM climate reports follow a climate-day convention based on midnight local standard time [1][3]. Since October 31, 2026, was still within Chicago's daylight saving period, this convention translates to a reporting interval of 1:00 AM to 1:00 AM local daylight time [1][3].
Sources (6)
  1. 1IEM:: Tabular CLI Report Datamesonet.agron.iastate.edu
  2. 2Kord26uspest.org
  3. 3IEM:: Tabular CLI Report Datamesonet.agron.iastate.edu
  4. 4Chicago high temperature rules: Kalshi at Midway (KMDW), Polymarket at KORD · Almanacalmanacmarket.com
  5. 5Highest temperature in Chicago on Oct 31, 2026?… | Frenzy Capitalfrenzycap.com
  6. 6Weather & Climate Prediction Markets — Live Odds | Frenzy Capitalfrenzycap.com

8. Which specific National Weather Service (NWS) report serves as the designated final data source for settling Kalshi's Chicago temperature markets?

Official Data SourceNWS Climatological Report (Daily), Chicago Midway (CLIMDW) [1][2]
Kalshi's Market BasisNational Weather Service reading for Chicago Midway Airport [3]
Settlement ReportNWS Climatological Report (Daily) [1]
The National Weather Service (NWS) Climatological Report (Daily) is Kalshi's official data source. This report, specifically the Chicago Midway (CLIMDW) version, serves as the designated final data source for settling Kalshi's daily Chicago temperature markets [1][2]. Kalshi's own explanations for weather markets confirm that Chicago daily high-temperature markets are based on National Weather Service readings for Chicago Midway Airport [3]. Kalshi's rules explicitly identify the NWS Climatological Report (Daily) as the official and final source for the day's high temperature [1].
Market settlement relies on specific NWS reports, not forecasts. For settlement purposes, users are directed to the NWS Weather Records/Climate interface where they must select "Chicago–Midway, IL" and "Daily Climate Report" [1]. This final NWS Daily Climate Report is issued after the observation date, typically the following morning, and is exclusively used for market settlement [1]. Notably, forecast data, preliminary readings, consumer weather applications, or information from The Weather Company are not considered for settling these markets [1].
Sources (3)
  1. 1Weather Markets | Kalshi Help Centerhelp.kalshi.com
  2. 2Lowest temperature in Chicago today? Odds & Predictions 2026kalshi.com
  3. 3Trading the weathernews.kalshi.com

9. How will the potential for post-day data corrections by the NWS affect the final settlement of the October 31, 2026 Chicago temperature market?

Governing Report for Chicago HighNWS Daily Climate Report (CLI) [1][2][3]
October 31, 2026 Market Settlement DateNovember 1, 2026 [4]
Kalshi Revision PolicyRevisions to underlying data made after expiration are not accounted for [5]
National Weather Service corrections can affect market settlement if documented promptly [6][5][4]. The final settlement of the October 31, 2026 Chicago temperature market could be influenced by post-day data corrections from the National Weather Service (NWS), provided these corrections are officially documented by the source agency prior to the market's settlement date [6][5][4]. The NWS Daily Climate Report (CLI), which governs the Chicago daily-high market, issues data that is preliminary until quality control procedures are fully completed [6][1]. NWS protocols explicitly permit later corrections to erroneous data through designated methods like Datzilla [6][2][3].
Market settlement relies on the source agency's data documented by expiration [5]. The Kalshi contract framework stipulates that the expiration value is determined by the source agency's value as it is documented at the precise expiration date and time [5]. For the October 31, 2026 Chicago temperature market, the designated settlement date is November 1, 2026 [4]. Consequently, any NWS data corrections pertaining to October 31, 2026, would be incorporated into the market's settlement if they are part of the source agency's value documented by November 1, 2026 [5][4]. Conversely, any revisions to the underlying data made after this official documentation would not be considered in determining the expiration value [5].
Sources (6)
  1. 1Weather Markets | Kalshi Help Centerhelp.kalshi.com
  2. 2Lowest temperature in Chicago today? Odds & Predictions 2026kalshi.com
  3. 3Highest temperature in Boston today? Odds & Predictions 2026kalshi.com
  4. 4Chicago Weather on Oct 31, 2026 | Prediction Market Forecastpredictmarketcap.com
  5. 5Sincerely,assets.kalshi.com
  6. 6Department of Commerce • National Oceanic & Atmospheric Administration • National Weather Serviceweather.gov

10. How does the observed October 31, 2026, high temperature at O'Hare compare against the NWS's historical climate data for the same date in Chicago?

Observed High Temperature (Oct 31, 2026)60–61°F [1]
1991–2020 Normal High (Oct 31)55.9°F [1][2][3]
Historical Record High (Oct 31)84°F (1950) [1][4]
The observed October 31, 2026, high temperature in Chicago exceeded the normal for the date. The recorded high of 60–61°F was warmer than the 1991–2020 normal high of 55.9°F for October 31 at Chicago O’Hare, specifically approximately 4–5°F above normal [1][2][4][3]. For additional context, the 1991–2020 normal low for this date is 40.1°F, resulting in a normal mean temperature of 48.0°F [2].
The observed high remained significantly below the historical record high. While above normal, the 60–61°F observed temperature was 23–24°F below the historical record high of 84°F for October 31, which was established in 1950 [1][4]. The NWS historical daily record table also identifies a record low maximum of 31°F for October 31, set in 1873 [4].
Official climate reporting sites differ from prediction market sources. O’Hare is recognized as the official Chicago observation site for NWS climate reporting [4]. However, the prediction market's settlement source for the October 31, 2026, temperature is Chicago CLIMDW/Weather Company, highlighting a distinction in reporting venues and sources [4][5][6].
Sources (6)
  1. 1Highest temperature in Chicago on Oct 31, 2026?… | Frenzy Capitalfrenzycap.com
  2. 2Chicago (O'Hare) 1991-2020 Climate Normalsweather.gov
  3. 3October Normals for Temperature, Precipitation and Snowfall for Chicago, ILweather.gov
  4. 4Chicago Climate Records and Rankingsweather.gov
  5. 5October 30-31, 2019: Snowiest Halloween on Record for Some; More Lakeshore Floodingweather.gov
  6. 6Chicago Weather on Oct 31, 2026 | Prediction Market Forecastpredictmarketcap.com

11. What Could Change the Odds

Key Catalysts

The pre-event forecast signaled warmth versus the Oct. 31 Chicago normal high of 56°F [1][2][3][4][5]. Chicago ran just over 6°F above average through Oct. 26 [1][2][4], setting a warm October background. Bullish catalysts included this warm regime, southerly flow, and forecasts near or above 60°F [1][2][3][4]. NWS’s Oct. 29 point matrix projected an O’Hare maximum of 60°F and Midway maximum of 61°F [1]. Weather Underground showed 62°F for O’Hare, about 60°F for downtown Chicago, and 71°F for one Midway-area page, indicating station/model dispersion [4][5].
Bearish catalysts centered on an approaching rain system, increasing cloud cover, and lake influence [1][2][3][4]. A shift from a prolonged dry spell toward scattered rain raised precipitation chances, generally 20–40% in the broader forecast, increasing into Halloween evening [1][2][4]. NWS’s O’Hare matrix showed Oct. 31 precipitation probabilities rising to 40% and then 70% in successive periods, which could cap daytime heating [1][2][4]. This forecast disagreement across O’Hare, downtown, and Midway contributed to uncertainty [1][2][3][4]. The highest-confidence pre-event range was roughly 60–63°F for O’Hare, with materially greater uncertainty for Midway-based contracts [1][2][3][4]. As of Oct. 31, 2026, Polymarket had the leading 60–61°F outcome at 39%, 58–59°F at 31%, and 62–63°F at 18% [4]. Kalshi’s pre-event distribution showed 41% for 62–63°F and 31% for 60–61°F [3].

Key Dates & Catalysts

  • Strike Date: November 01, 2026
  • Expiration: November 07, 2026
  • Closes: November 01, 2026
Sources (5)
  1. 1National Weather Serviceforecast.weather.gov
  2. 2Nothing too scary about Chicago's Halloween forecasttheweather.com
  3. 3Highest temperature in Chicago tomorrow? Odds & Predictions 2026kalshi.com
  4. 4Highest temperature in Chicago on October 31?polymarket.com
  5. 5October 31, 2026: Chicago Daily Temperature High October 31 2026 Prediction Marketrobinhood.com

13. Historical Resolutions

Historical Resolutions: 20 markets in this series

Outcomes: 3 resolved YES, 17 resolved NO

Recent resolutions:

  • KXHIGHCHI-26OCT29-T75: NO (Oct 30, 2026)
  • KXHIGHCHI-26OCT29-T68: NO (Oct 30, 2026)
  • KXHIGHCHI-26OCT29-B74.5: NO (Oct 30, 2026)
  • KXHIGHCHI-26OCT29-B72.5: NO (Oct 30, 2026)
  • KXHIGHCHI-26OCT29-B70.5: NO (Oct 30, 2026)