Recent National Weather Service guidance and ensemble model runs indicate a cool northeasterly flow advecting drier, stable air into the Chicago region, limiting daytime heating and producing overnight lows in the mid-to-upper 50s for September 21. Persistent cloud cover from upstream showers reduces radiative cooling overnight while also suppressing maximum temperatures near 64–65°F, narrowing the expected diurnal range. Historical September climatology shows average lows near 56°F, yet current conditions favor values clustered around 58–61°F, with market-implied odds reflecting modest spread across model solutions and uncertainty in exact wind speeds and moisture advection timing ahead of the next forecast update.
Experimental AI-generated summary referencing Polymarket data. This is not trading advice and plays no role in how this market resolves. · UpdatedLowest temperature in Chicago on September 21?
Lowest temperature in Chicago on September 21?
60-61°F 31%
58-59°F 22%
56-57°F 19%
62-63°F 19%
NEW
NEW
Sep 21, 2026
49°F or below
5%
50-51°F
5%
52-53°F
7%
54-55°F
10%
56-57°F
19%
58-59°F
22%
60-61°F
31%
62-63°F
19%
64-65°F
10%
66-67°F
7%
68°F or higher
5%
60-61°F 31%
58-59°F 22%
56-57°F 19%
62-63°F 19%
NEW
NEW
Sep 21, 2026
49°F or below
$0 Vol.
5%
50-51°F
$0 Vol.
5%
52-53°F
$0 Vol.
7%
54-55°F
$0 Vol.
10%
56-57°F
$0 Vol.
19%
58-59°F
$0 Vol.
22%
60-61°F
$0 Vol.
31%
62-63°F
$0 Vol.
19%
64-65°F
$0 Vol.
10%
66-67°F
$0 Vol.
7%
68°F or higher
$0 Vol.
5%
This market will resolve to the temperature range that contains the lowest temperature recorded by NOAA at the Chicago O'Hare Intl Airport Station in degrees Fahrenheit on 21 Sep '26.
The resolution source for this market will be information from NOAA, specifically the lowest reading under the "Temp" column for all times on this day, available here: https://www.weather.gov/wrh/timeseries?site=kord
This market will resolve off of the Hourly Data provided using the "Show Hourly Data" button.
If NOAA data for the observation date is unavailable by 11:59 PM ET on the day following the observation date, the Weather Underground Daily Observations table will be used as the resolution source.
In the event that there is no data for the observation date by 11:59 PM ET on the day following the observation date, this market will resolve to the lowest bracket.
To toggle between Fahrenheit and Celsius, click the "Switch to US Units w/ kts" button until the relevant table displays °F.
This market will resolve once the first data point for the following date has been published on the resolution source, or by 11:59 PM ET on the day following the observation date, whichever comes first.
The resolution source for this market measures temperatures to whole degrees Fahrenheit (eg, 21°F). Thus, this is the level of precision that will be used when resolving the market.
Revisions to temperatures recorded within this market's timeframe will be considered until the first datapoint for the following date has been published, after which any alterations will not be considered.Recent National Weather Service guidance and ensemble model runs indicate a cool northeasterly flow advecting drier, stable air into the Chicago region, limiting daytime heating and producing overnight lows in the mid-to-upper 50s for September 21. Persistent cloud cover from upstream showers reduces radiative cooling overnight while also suppressing maximum temperatures near 64–65°F, narrowing the expected diurnal range. Historical September climatology shows average lows near 56°F, yet current conditions favor values clustered around 58–61°F, with market-implied odds reflecting modest spread across model solutions and uncertainty in exact wind speeds and moisture advection timing ahead of the next forecast update.
This market will resolve to the temperature range that contains the lowest temperature recorded by NOAA at the Chicago O'Hare Intl Airport Station in degrees Fahrenheit on 21 Sep '26.
The resolution source for this market will be information from NOAA, specifically the lowest reading under the "Temp" column for all times on this day, available here: https://www.weather.gov/wrh/timeseries?site=kord
This market will resolve off of the Hourly Data provided using the "Show Hourly Data" button.
If NOAA data for the observation date is unavailable by 11:59 PM ET on the day following the observation date, the Weather Underground Daily Observations table will be used as the resolution source.
In the event that there is no data for the observation date by 11:59 PM ET on the day following the observation date, this market will resolve to the lowest bracket.
To toggle between Fahrenheit and Celsius, click the "Switch to US Units w/ kts" button until the relevant table displays °F.
This market will resolve once the first data point for the following date has been published on the resolution source, or by 11:59 PM ET on the day following the observation date, whichever comes first.
The resolution source for this market measures temperatures to whole degrees Fahrenheit (eg, 21°F). Thus, this is the level of precision that will be used when resolving the market.
Revisions to temperatures recorded within this market's timeframe will be considered until the first datapoint for the following date has been published, after which any alterations will not be considered.
The resolution source for this market will be information from NOAA, specifically the lowest reading under the "Temp" column for all times on this day, available here: https://www.weather.gov/wrh/timeseries?site=kord
This market will resolve off of the Hourly Data provided using the "Show Hourly Data" button.
If NOAA data for the observation date is unavailable by 11:59 PM ET on the day following the observation date, the Weather Underground Daily Observations table will be used as the resolution source.
In the event that there is no data for the observation date by 11:59 PM ET on the day following the observation date, this market will resolve to the lowest bracket.
To toggle between Fahrenheit and Celsius, click the "Switch to US Units w/ kts" button until the relevant table displays °F.
This market will resolve once the first data point for the following date has been published on the resolution source, or by 11:59 PM ET on the day following the observation date, whichever comes first.
The resolution source for this market measures temperatures to whole degrees Fahrenheit (eg, 21°F). Thus, this is the level of precision that will be used when resolving the market.
Revisions to temperatures recorded within this market's timeframe will be considered until the first datapoint for the following date has been published, after which any alterations will not be considered.
Market Opened: Sep 19, 2026, 3:29 AM ET
Volume
$0End Date
Sep 21, 2026Market Opened
Sep 19, 2026, 3:29 AM ETResolution Source
https://www.weather.gov/wrh/timeseries?site=kordResolver
0x69c47De9D...This market will resolve to the temperature range that contains the lowest temperature recorded by NOAA at the Chicago O'Hare Intl Airport Station in degrees Fahrenheit on 21 Sep '26.
The resolution source for this market will be information from NOAA, specifically the lowest reading under the "Temp" column for all times on this day, available here: https://www.weather.gov/wrh/timeseries?site=kord
This market will resolve off of the Hourly Data provided using the "Show Hourly Data" button.
If NOAA data for the observation date is unavailable by 11:59 PM ET on the day following the observation date, the Weather Underground Daily Observations table will be used as the resolution source.
In the event that there is no data for the observation date by 11:59 PM ET on the day following the observation date, this market will resolve to the lowest bracket.
To toggle between Fahrenheit and Celsius, click the "Switch to US Units w/ kts" button until the relevant table displays °F.
This market will resolve once the first data point for the following date has been published on the resolution source, or by 11:59 PM ET on the day following the observation date, whichever comes first.
The resolution source for this market measures temperatures to whole degrees Fahrenheit (eg, 21°F). Thus, this is the level of precision that will be used when resolving the market.
Revisions to temperatures recorded within this market's timeframe will be considered until the first datapoint for the following date has been published, after which any alterations will not be considered.Recent National Weather Service guidance and ensemble model runs indicate a cool northeasterly flow advecting drier, stable air into the Chicago region, limiting daytime heating and producing overnight lows in the mid-to-upper 50s for September 21. Persistent cloud cover from upstream showers reduces radiative cooling overnight while also suppressing maximum temperatures near 64–65°F, narrowing the expected diurnal range. Historical September climatology shows average lows near 56°F, yet current conditions favor values clustered around 58–61°F, with market-implied odds reflecting modest spread across model solutions and uncertainty in exact wind speeds and moisture advection timing ahead of the next forecast update.
This market will resolve to the temperature range that contains the lowest temperature recorded by NOAA at the Chicago O'Hare Intl Airport Station in degrees Fahrenheit on 21 Sep '26.
The resolution source for this market will be information from NOAA, specifically the lowest reading under the "Temp" column for all times on this day, available here: https://www.weather.gov/wrh/timeseries?site=kord
This market will resolve off of the Hourly Data provided using the "Show Hourly Data" button.
If NOAA data for the observation date is unavailable by 11:59 PM ET on the day following the observation date, the Weather Underground Daily Observations table will be used as the resolution source.
In the event that there is no data for the observation date by 11:59 PM ET on the day following the observation date, this market will resolve to the lowest bracket.
To toggle between Fahrenheit and Celsius, click the "Switch to US Units w/ kts" button until the relevant table displays °F.
This market will resolve once the first data point for the following date has been published on the resolution source, or by 11:59 PM ET on the day following the observation date, whichever comes first.
The resolution source for this market measures temperatures to whole degrees Fahrenheit (eg, 21°F). Thus, this is the level of precision that will be used when resolving the market.
Revisions to temperatures recorded within this market's timeframe will be considered until the first datapoint for the following date has been published, after which any alterations will not be considered.
The resolution source for this market will be information from NOAA, specifically the lowest reading under the "Temp" column for all times on this day, available here: https://www.weather.gov/wrh/timeseries?site=kord
This market will resolve off of the Hourly Data provided using the "Show Hourly Data" button.
If NOAA data for the observation date is unavailable by 11:59 PM ET on the day following the observation date, the Weather Underground Daily Observations table will be used as the resolution source.
In the event that there is no data for the observation date by 11:59 PM ET on the day following the observation date, this market will resolve to the lowest bracket.
To toggle between Fahrenheit and Celsius, click the "Switch to US Units w/ kts" button until the relevant table displays °F.
This market will resolve once the first data point for the following date has been published on the resolution source, or by 11:59 PM ET on the day following the observation date, whichever comes first.
The resolution source for this market measures temperatures to whole degrees Fahrenheit (eg, 21°F). Thus, this is the level of precision that will be used when resolving the market.
Revisions to temperatures recorded within this market's timeframe will be considered until the first datapoint for the following date has been published, after which any alterations will not be considered.
Volume
$0End Date
Sep 21, 2026Market Opened
Sep 19, 2026, 3:29 AM ETResolution Source
https://www.weather.gov/wrh/timeseries?site=kordResolver
0x69c47De9D...Recent National Weather Service guidance and ensemble model runs indicate a cool northeasterly flow advecting drier, stable air into the Chicago region, limiting daytime heating and producing overnight lows in the mid-to-upper 50s for September 21. Persistent cloud cover from upstream showers reduces radiative cooling overnight while also suppressing maximum temperatures near 64–65°F, narrowing the expected diurnal range. Historical September climatology shows average lows near 56°F, yet current conditions favor values clustered around 58–61°F, with market-implied odds reflecting modest spread across model solutions and uncertainty in exact wind speeds and moisture advection timing ahead of the next forecast update.
Experimental AI-generated summary referencing Polymarket data. This is not trading advice and plays no role in how this market resolves. · Updated
Beware of external links.
Beware of external links.
Frequently Asked Questions