Highest temperature in Chicago on Oct 9, 2026?
Short Answer
The highest temperature in Chicago on Oct 9, 2026, is a toss-up to be 70°F or below (market 53%), as specific forecasts from WGN and WiseMeteo point to 73-74°F and Weather Underground to 71°F, despite cooler historical averages.
1. Market Behavior & Drivers
The market's largest move, a 15.0 percentage point spike on October 9, lacks a specific driver identified in the available research. This final jump to a 55.0% probability occurred on the day of the temperature reading itself. While local reports anticipated afternoon showers and a possible thunderstorm, no single news item or update appears to account for the magnitude of the last-minute shift.
The preceding upward momentum was directly caused by official weather forecasts released on October 8. Probabilities gained 10.0 percentage points after Weather Underground predicted a high of 71°F and FOX 32 reported highs in the "low 70s." These forecasts aligned with the market's specific 71°F contract, pulling sentiment away from a competing contract for a higher temperature range ("73° to 74°"). High trading volume on the final day supports the conviction behind the market's closing price.
- The market's favored outcome below 71°F is countered by a specific 71°F forecast.
- The 71-72°F range gains support from the settlement source's 71°F forecast.
- WGN and WiseMeteo forecasts indicate a 73-74°F high, suggesting unseasonably mild conditions.
Current Context
Chicago forecasts predict a mild October 9, above historical averages. Forecasts for October 9, 2026, indicate a high around 71–74°F for Chicago, with afternoon showers and possibly an isolated thunderstorm expected [1][2][3]. Weather Underground forecast 71°F, WGN called for 74°F, and FOX 32 described highs in the low 70s [1][2][3]. This range exceeds the historical October 9 average high of 66.5–66.7°F [4][5][6]. The all-time high for October 9 was 87°F, set in 2010, while the lowest daily high recorded was 43°F in 1964 [5].
Prediction markets show varied sentiment; official observation data is pending. Prediction markets for the October 9, 2026, high temperature exhibit divergent probabilities. Kalshi quoted approximately 56% for 70°F or below, 26% for 71–72°F, and 15% for 73–74°F [7]. A Polymarket tracker showed 72–73°F as the leading range at 38.6%, while another market summary reported 70–71°F at 43.5% [8][9]. These figures represent market probabilities, not verified observations [7][8][9]. An official observed maximum temperature for October 9, 2026, was not available in retrieved NOAA/NWS material; the NWS climate file, retrieved early Friday, reported October 8's O'Hare maximum as 73°F and listed only October 9 normals and records [1][10]. NOAA's indexed daily data for the relevant O'Hare climate station (GHCND:USW00094846) ended October 3 in the retrieved result [10].
Resolution definitions for "Chicago high" vary by market venue. The precise definition of "Chicago high" is station-dependent and varies among prediction markets. O'Hare-based markets generally specify NOAA hourly observations and whole-degree Fahrenheit brackets for resolution [7][8]. Conversely, the Robinhood/Forecastex contract specifies Chicago Midway International Airport (KMDW) daily observations from Weather Underground [11][12].
Sources (12)
- 1https://tgftp.nws.noaa.gov/data/climate/daily/il/chicago.txttgftp.nws.noaa.gov
- 2Friday: Unseasonably mild with sun and cloudswgntv.com
- 3Chicago weather: Rain and storms possible today before a lovely weekend | FOX 32 Chicagofox32chicago.com
- 4October 9 - Chicago - Weather History and Averages - Overcast Dataovercastdata.com
- 5Chicago October 9 Weather Recordsextremeweatherwatch.com
- 6IEM:: CLI from NWS LOTmesonet1.agron.iastate.edu
- 7Highest temperature in Chicago tomorrow? - Kalshikalshi.com
- 8Highest temperature in Chicago on October 9? - Polymarket Odds | CoinRithmcoinrithm.com
- 9Highest temperature in Chicago on October 9?alphio.ai
- 10Daily Summaries Station Details: CHICAGO OHARE INTERNATIONAL AIRPORT, IL US, GHCND:USW00094846 | Climate Data Online (CDO) | National Climatic Data Center (NCDC)ncei.noaa.gov
- 11Highest temperature in Chicago on October 9? - Polymarketpolymarket.us
- 12Chicago Daily Temperature High October 9 2026 - Robinhoodrobinhood.com
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.
Outcome: 70° or below
📈 October 09, 2026: 15.0pp spike
Price increased from 40.0% to 55.0%
What happened: The provided web research did not surface any social media activity from key figures or viral narratives that could account for the 15.0 percentage point spike in the prediction market. The only weather-related news identified was a possible band of showers and thunderstorms across Chicago on October 9, 2026, though coverage was expected to be low due to dry air [1]. This limited information, without timing relative to the market spike or stronger impact, does not provide a definitive primary driver. Therefore, social media was irrelevant based on the available data.
Outcome: 73° to 74°
📉 October 08, 2026: 11.0pp drop
Price decreased from 27.0% to 16.0%
What happened: The 11.0 percentage point drop in the "73° to 74°" outcome was primarily driven by updated official weather forecasts available on October 8, 2026, for the following day. Weather Underground notably predicted a high of 71°F, and FOX 32 reported "low 70s" for October 9, which fell below or at the very low end of the 73-74°F range [2]. This collectively lowered market confidence in the specific 73-74°F outcome. Social media activity, such as a local meteorologist's post forecasting "low 70s" for October 9, appeared on October 9 and therefore lagged the market movement [3]. Social media was mostly noise or irrelevant to this specific price drop.
Sources (3)
- 1Band of Showers and Storms Could Cross Chicago, O’Hare, and Gary Friday Afternoon in Northern Illinois and Indiana Though Coverage Stays Low – Seven Lakes Newssevenlakes.news
- 2Chicago weather: Rain and storms possible today before a lovely weekend | FOX 32 Chicagofox32chicago.com
- 3Chicago & Suburbs (10/9/26): A few showers are around today...facebook.com
4. Market Data
Contract Snapshot
This market resolves based on the highest temperature recorded in Chicago today. A "YES" resolution occurs if the highest temperature falls within the specific range of the contract; otherwise, it resolves "NO." While generally based on today's data, expiration may be delayed if a material error is found in the initial non-preliminary publication, pending a data revision or the market's Expiration Date, whichever comes first. If no data is available at the end of this period, markets will resolve to the last fair price determined by Kalshi.
Market Discussion
Weather forecasts for Chicago on October 9, 2026, projected high temperatures primarily in the low-to-mid 70s, with WGN forecasting approximately 74°F [1] and another outlook specifying 73°F [2]. Prediction market pricing across platforms such as Kalshi, Polymarket, and Alphio generally clustered around the low-to-mid 70s, with leading bins including 71–72°F [3], 72–73°F [4], and 70–71°F [5]. The specific highest temperature will depend on the weather station and source designated for settlement by each market, such as NOAA's Chicago O'Hare International Airport station (KORD) for Polymarket or the Weather Underground Chicago Midway International Airport station (KMDW) for Robinhood [4][6].
Sources (6)
- 1Friday: Unseasonably mild with sun and cloudswgntv.com
- 2Chicago - weather outlook for 9 October 2026wisemeteo.com
- 3Highest temperature in Chicago on Oct 9, 2026? - Compare Kalshi vs Gemini Odds | CoinRithmcoinrithm.com
- 4Highest temperature in Chicago on October 9? - Polymarket Odds | CoinRithmcoinrithm.com
- 5Highest temperature in Chicago on October 9? - Alphio AIalphio.ai
- 6Chicago Daily Temperature High October 9 2026 - Robinhoodrobinhood.com
5. Trust Index
Integrity risk· Resolution quality
How it adds up
Integrity80% of score72Good
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 score32High Risk
Includes the cost to trade: a $1,000 order can't be filled here because the order book is too thin.
Trust score64Caution
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
6. How have the official daily high temperatures at Chicago's O'Hare (KORD) and Midway (KMDW) airports differed on October 9 over the past decade?
| O'Hare High Temperature (Oct 9, 2025) | 64°F [1] |
|---|---|
| O'Hare Normal High (Oct 9, 1991-2020) | 65.8°F [2][3] |
| Daily High Temp Data Availability (2016-2025) | Not reliably calculable for the full period [2][3][4][5][6] |
Reliable decade-long temperature differences for Chicago airports cannot be determined. The exact series of differences in official daily high temperatures at Chicago's O'Hare (KORD) and Midway (KMDW) airports on October 9 over the past decade cannot be reliably calculated from the provided sources [2][3]. The available evidence does not include the ten annual paired observations required, nor does it provide a complete October 9 year-by-year table for both airports covering 2016–2025 [2][3][4][5][6]. Official daily climatological reports are provided separately by the National Weather Service for O'Hare (ORD/KORD) and Midway (MDW/KMDW), indicating that comparisons of airport highs should be made station-by-station rather than consolidating into a single Chicago observation [7][8][9].
Specific temperature data is available for O'Hare on particular dates. On October 9, 2025, Chicago-O'Hare (KORD) recorded a high of 64°F, according to its October 2025 report [1]. The 1991–2020 official Chicago/O'Hare normal high for October 9 is 65.8°F [2][3]. For an October 9, 2026 prediction-market, Chicago-Midway (KMDW) is identified as the relevant station; however, the provided evidence only supports a pre-resolution context and does not establish the official realized October 9, 2026 high [10][11][12].
Sources (12)
- 1National Weather Serviceforecast.weather.gov
- 2Chicago (O'Hare) 1991-2020 Climate Normalsweather.gov
- 3October Normals for Temperature, Precipitation and Snowfall for Chicago, ILweather.gov
- 4October 2025 Climate Summary - National Weather Serviceweather.gov
- 5October 2024 Climate Summaryweather.gov
- 62024 Calendar Year Climate Summaryweather.gov
- 7Chicago - National Weather Serviceforecast.weather.gov
- 8Climatological Report (Daily) - National Weather Serviceforecast.weather.gov
- 9Climatological Report (Daily) - National Weather Serviceforecast.weather.gov
- 10Highest temperature in Chicago on October 9, 2026? - Compare probabilidades: Gemini vs Kalshi | CoinRithmcoinrithm.com
- 11Chicago Daily Temperature High October 9 2026 - Robinhoodrobinhood.com
- 12Kalshi Climate and Weather Odds Today: 228 Open Markets | Kalshi Viewkalshiview.com
7. What does recent historical data (2023-2025) indicate about the 3-day-out forecast accuracy of the NWS versus commercial services like Weather Underground for early October highs in Chicago?
| Data needed for comparison | Archived T-3 forecasts for October 9, issued around October 6-7 [1][2][3] |
|---|---|
| Target observation location | Chicago Midway [4] |
| Verifying data source | NOAA/NWS daily climate data [4] |
Direct comparison of 3-day-out forecast accuracy is currently not feasible. A numerical evaluation of 3-day-out forecast accuracy for Chicago's early October highs (specifically October 9) between the National Weather Service (NWS) and commercial services such as Weather Underground for the 2023–2025 period cannot be reliably conducted at this time [3][5][6][7]. This limitation stems from an insufficient quantity of accessible data required to facilitate a robust and dependable comparative analysis [3][5][6][7].
Archived daily forecast data is currently unavailable from sources. NWS pages provide generalized climate summaries and seasonal normals, rather than specific, timestamped historical forecasts issued days in advance [3][5][6][7]. Similarly, Weather Underground offers historical observations and calendar data but lacks the exact 3-day-out (T-3) forecasts that would have been published for the target dates [3][5][6][7]. Consequently, without access to these specific historical forecast snapshots, a direct comparison of predicted high temperatures against their corresponding actual observations cannot be performed [1][2][3].
Reconstructing historical forecasts would enable a comprehensive accuracy study. To conduct a reliable investigation, it would be necessary to retrieve and analyze archived forecasts specifically issued around October 6–7 for the October 9 target date in each year. This process would involve extracting each service's predicted high temperature and calculating its absolute error when compared against the observed high. The verifying observed temperature should be specifically from Chicago Midway, sourced from NOAA/NWS daily climate data [4]. Additionally, careful consideration must be given to the selection of the Weather Underground station, as its Chicago pages may present different high temperatures from various reporting sites [4][8].
Sources (8)
- 1October 2025 Climate Summary - National Weather Serviceweather.gov
- 2October 2023 Climate Recap - Chicagoweather.gov
- 3October 2024 Climate Summaryweather.gov
- 4Past Weather - National Centers for Environmental Informationncei.noaa.gov
- 5October Normals for Temperature, Precipitation and Snowfall for Chicago, ILweather.gov
- 6Highest temperature in Chicago on October 9, 2026? - Compare probabilidades: Gemini vs Kalshi | CoinRithmcoinrithm.com
- 7Kalshi Climate and Weather Odds Today: 228 Open Markets | Kalshi Viewkalshiview.com
- 8Chicago, IL Weather Historywunderground.com
8. What specific short-term weather patterns, like an amplified jet stream ridge or an early cold front, are long-range models from the ECMWF and GFS monitoring for the week of October 9, 2026?
| October 9, 2026 Validation | Not directly validated by long-range models (ECMWF, GEFS ensemble means) [1] |
|---|---|
| CPC 6-10 Day Window Start | October 14 [1] |
| ECMWF Forecast Range | Up to 15 days [2] |
Long-range models lack specific features for October 9, 2026. As of current analyses, long-range models from the ECMWF and GEFS ensemble means do not directly validate any day-specific synoptic features for October 9, 2026. Similarly, the published Climate Prediction Center (CPC) discussion does not validate a specific cold front or ridge passage for Chicago on October 9, as its 6–10-day forecast window commences on October 14 [1].
Broader patterns are indicated for mid-October, not early October. NOAA's CPC reports that the 0Z ECMWF and GEFS ensemble means show agreement on a broad North American pattern for the period of October 14–18. This pattern is characterized by an amplified trough over the Aleutians/North Pacific, downstream ridging extending from western Canada into the northwestern and north-central United States, and positive height anomalies across much of the eastern United States [1][3]. While a later probabilistic hazards outlook describes a Week 2 scenario with a mean surface low crossing the upper Midwest, this represents a later-developing signal and does not confirm a specific front reaching Chicago on October 9 [4].
Long-range forecasts for October 9, 2026, inherently carry high uncertainty. Precise daily high temperatures or exact frontal timing for Chicago on October 9, 2026, are subject to significant uncertainty due to the extended lead time. ECMWF medium-range ensemble forecasts are designed to provide probabilities out to 15 days, and GFS products typically extend for approximately 15–16 days. At such long ranges, factors like ensemble spread and run-to-run changes inherently contribute to the forecast's uncertainty [2][5][6].
Sources (6)
- 1Climate Prediction Center - 6-10 and 8-14 Day Prognostic Discussionscpc.ncep.noaa.gov
- 2Medium-range forecasts | ECMWFecmwf.int
- 3Climate Prediction Center - 6-10 and 8-14 Day Prognostic Discussionscpc.ncep.noaa.gov
- 4Probabilistic Hazards Outlook - Climate Prediction Center - NOAAcpc.ncep.noaa.gov
- 5Open data - ECMWFecmwf.int
- 6Model charts for Illinois (Temperature) | GFS (15 days)weather.us
9. What is the official NOAA/NWS data source and publication schedule for the daily maximum temperature at Chicago O'Hare (GHCND:USW00094846) that will be used for market resolution?
| Official data source | NWS Daily Climate Report (CLI) [1][2] |
|---|---|
| Full-day report publication time | Shortly after 12:30 AM local time (CST/CDT) [1] |
| GHCNd data availability | 45–60 days after month-end [2][3] |
The official daily maximum temperature source is the NWS Daily Climate Report. For the daily maximum temperature at Chicago O'Hare (GHCND:USW00094846), the first published full-day National Weather Service (NWS) Daily Climate Report (CLI) is the designated source, identified as ORD/CLI from WFO Chicago [1][2][4]. This report provides the authoritative operational data for the calendar-day maximum temperature at the official Chicago O'Hare Airport observation site, with temperatures reported in degrees Fahrenheit [1][4]. The NWS Chicago office issues the CLI twice daily, and the complete full-day summary is typically available shortly after 12:30 AM local time (CST/CDT) following the calendar day [1].
The GHCNd dataset offers archival data but is not real-time. While the Global Historical Climatology Network daily (GHCNd) dataset also corresponds to GHCND:USW00094846, it serves primarily for archival cross-checking and is not considered the most expedient source for same-day data resolution [2][5][3]. GHCNd follows a distinct NOAA/NCEI data-publication schedule; daily updates incorporate observations from both the current and previous day, and archive-ready replacement data typically become available 45 to 60 days after the conclusion of the month [2][3].
Sources (5)
10. According to NOAA's climate data, how frequently has the October 9 high temperature in Chicago fallen into the key market brackets of 70° or below, 71-74°, and 75° or above since 2000?
| Data completeness for frequency calculation | Incomplete (since 2000) [1][2] |
|---|---|
| Data required for calculation | NOAA/NCEI daily observations for Oct 9, 2000-2025 [1][3][4][5][6][7] |
| Prediction market resolution source | NWS Daily Climatological Report for Chicago-Midway [1][3][4][5][8][9] |
Specific October 9 temperature frequencies in Chicago cannot be determined from available data. The provided research findings do not expose the complete year-by-year October 9 observations necessary to calculate the frequency of Chicago's high temperatures since 2000 [1][2]. Consequently, specific frequencies for temperatures falling into the key market brackets of 70° or below, 71-74°, and 75° or above cannot be determined from the available information.
Calculating frequencies requires specific NOAA/NCEI daily observations for Chicago-Midway. A defensible frequency calculation for the Chicago-Midway (MDW) station would necessitate downloading NOAA/NCEI daily observations for October 9 from 2000 through 2025 [1][3][4][5][6][7]. This process would involve counting the maximum temperature (TMAX) values that fall within the defined brackets. Prediction markets commonly use the NWS Daily Climatological Report for Chicago-Midway for resolution, with underlying daily maximum temperature records sourced from NOAA Climate Data Online and NWS climate products [1][3][4][5][8][9].
Sources (9)
- 1Chicago Climate Records and Rankingsweather.gov
- 2October Temperature Records for American Institute Of Drafting...weatherforyou.com
- 3Chicago - National Weather Serviceforecast.weather.gov
- 4WFO Monthly/Daily Climate Data - National Weather Serviceforecast.weather.gov
- 5Search | Climate Data Online (CDO)ncdc.noaa.gov
- 6U.S. Climate Normalsncei.noaa.gov
- 7IEM:: Download ASOS/AWOS/METAR Data - Iowa Mesonetmesonet.agron.iastate.edu
- 8Highest temperature in Chicago on October 9, 2026? - Compare probabilidades: Gemini vs Kalshi | CoinRithmcoinrithm.com
- 9Kalshi Climate and Weather Odds Today: 228 Open Markets | Kalshi Viewkalshiview.com
11. What Could Change the Odds
Key Catalysts
For Chicago on October 9, 2026, the best available same-day forecast and market evidence pointed to a high in the low-to-mid 70s°F [1][2][3]. WGN forecast 74°F, FOX 32 said low 70s, and WiseMeteo forecast 73°F [1][2][4]. The Polymarket distribution at 16:27 UTC favored 70–71°F (40%), followed by 68–69°F (25%) and 72–73°F (23%) [3]. Principal bullish catalysts for an above-consensus Chicago high included an unseasonably mild setup, southerly winds, and weekend warmth; WGN described highs about 8°F above normal [2].
The primary bearish catalysts were cloud cover, afternoon showers or isolated thunderstorms, and possible rain-driven cooling [1][2]. WGN and FOX 32 both highlighted precipitation/storm chances during the day [1][2]. Alternative forecast sources were somewhat cooler or aligned near 73°F, with Weather Underground showing 71°F and WiseMeteo showing 73°F; this created meaningful uncertainty around the exact settlement temperature [5][4]. The market read was mildly bullish for 72–73°F or broader low-to-mid-70s outcomes relative to the historical October 9 normal, but not strongly bullish for extreme warmth or a record, due to these downside risks [1][5][2][4][3]. October 9 Chicago climatology is materially cooler than the 2026 forecast, with an average high of about 66.7°F [6][7].
Key Dates & Catalysts
- Strike Date: October 10, 2026
- Expiration: October 16, 2026
- Closes: October 10, 2026
Sources (7)
- 1Friday: Unseasonably mild with sun and cloudswgntv.com
- 2Chicago weather: Rain and storms possible today before a lovely weekend | FOX 32 Chicagofox32chicago.com
- 3Highest temperature in Chicago on October 9? - Polymarketpolymarket.com
- 4Chicago - weather outlook for 9 October 2026wisemeteo.com
- 5Chicago, IL Hourly Weather Forecast | Weather Undergroundwunderground.com
- 6Chicago October 9 Weather Recordsextremeweatherwatch.com
- 7October 9 - Chicago - Weather History and Averages - Overcast Dataovercastdata.com
13. Historical Resolutions
Historical Resolutions: 20 markets in this series
Outcomes: 3 resolved YES, 17 resolved NO
Recent resolutions:
- KXHIGHCHI-26OCT08-T75: NO (Oct 09, 2026)
- KXHIGHCHI-26OCT08-T68: NO (Oct 09, 2026)
- KXHIGHCHI-26OCT08-B74.5: NO (Oct 09, 2026)
- KXHIGHCHI-26OCT08-B72.5: YES (Oct 09, 2026)
- KXHIGHCHI-26OCT08-B70.5: NO (Oct 09, 2026)
