**SPC Day 1 convective outlooks issued September 4, 2026, placed a Slight Risk of severe thunderstorms across the southern Great Lakes into the mid/upper Ohio Valley and mid-Atlantic, driven by a frontal zone and northwesterly flow aloft.** Tornado probabilities remained low, with a 2% contour covering parts of central Ohio and adjacent Indiana, while broader areas saw 5–15% damaging wind and 5% hail risks. Official NWS surveys confirmed tornadoes the prior day (September 3) in Detroit (peak winds ~115 mph) and Seneca County, New York, but no comparable confirmed events were highlighted for September 4 itself amid ongoing clusters favoring straight-line winds. Model consensus emphasized organized thunderstorm clusters capable of gusts to 70 mph overnight, with limited rotation potential due to modest low-level shear. Traders monitoring resolution criteria—such as any SPC-defined tornado watch or verified reports within city boundaries—would next watch updated Day 2 outlooks and real-time mesoscale discussions from the Storm Prediction Center for shifts in instability or shear.
Experimental AI-generated summary referencing Polymarket data. This is not trading advice and plays no role in how this market resolves. · UpdatedWhich cities face tornado risk on September 4?
Chicago, IL
<1%
Houston, TX
<1%
San Antonio, TX
<1%
Dallas, TX
<1%
Austin, TX
<1%
Fort Worth, TX
<1%
Columbus, OH
100%
Charlotte, NC
<1%
Indianapolis, IN
<1%
Denver, CO
<1%
Nashville, TN
<1%
Oklahoma City, OK
<1%
Memphis, TN
<1%
Louisville, KY
<1%
Atlanta, GA
<1%
Kansas City, MO
<1%
Omaha, NE
<1%
Minneapolis, MN
<1%
Wichita, KS
<1%
New Orleans, LA
<1%
Tampa, FL
<1%
St. Louis, MO
<1%
Birmingham, AL
<1%
Des Moines, IA
<1%
Little Rock, AR
<1%
$8,497 Vol.
Chicago, IL
<1%
Houston, TX
<1%
San Antonio, TX
<1%
Dallas, TX
<1%
Austin, TX
<1%
Fort Worth, TX
<1%
Columbus, OH
100%
Charlotte, NC
<1%
Indianapolis, IN
<1%
Denver, CO
<1%
Nashville, TN
<1%
Oklahoma City, OK
<1%
Memphis, TN
<1%
Louisville, KY
<1%
Atlanta, GA
<1%
Kansas City, MO
<1%
Omaha, NE
<1%
Minneapolis, MN
<1%
Wichita, KS
<1%
New Orleans, LA
<1%
Tampa, FL
<1%
St. Louis, MO
<1%
Birmingham, AL
<1%
Des Moines, IA
<1%
Little Rock, AR
<1%
The SPC Day 1 Convective Outlook assigns tornado probability percentages (2%, 5%, 10%, etc.) to geographic areas across the US. If the city's coordinates fall inside any area rated 2% or higher, that city resolves "Yes". If a city is outside all tornado probability areas, or only within areas rated below 2%, that city resolves "No".
The SPC outlook is published as machine-readable geographic data (GeoJSON) at spc.noaa.gov. Each city's coordinates and the polygon boundaries are publicly verifiable. Borderline cases can be independently confirmed using the polygon data (excluding the hatched SIGN overlay, which is not a probability rating) and the city's listed coordinates. The point-in-polygon test is performed on unprojected WGS84 (EPSG:4326) coordinates, which is the native coordinate system of the SPC GeoJSON data.
Resolution is based on the scheduled 01:00 UTC Day 1 Convective Outlook update issued on the following UTC calendar day. The SPC Day 1 outlook covers a 24-hour period from 12:00 UTC to 12:00 UTC the following day. Subsequent revisions published after that scheduled update will not be considered. If the SPC outlook is not published or is unavailable, the market remains open until data is available.
The resolution source for this market is the NOAA Storm Prediction Center at spc.noaa.gov.
This market uses coordinates 41.8781, -87.6298 for Chicago, IL.
Market Opened: Sep 4, 2026, 8:13 AM ET
Resolution Source
https://www.spc.noaa.gov/products/outlook/day1otlk.htmlResolver
0x65070BE91...The SPC Day 1 Convective Outlook assigns tornado probability percentages (2%, 5%, 10%, etc.) to geographic areas across the US. If the city's coordinates fall inside any area rated 2% or higher, that city resolves "Yes". If a city is outside all tornado probability areas, or only within areas rated below 2%, that city resolves "No".
The SPC outlook is published as machine-readable geographic data (GeoJSON) at spc.noaa.gov. Each city's coordinates and the polygon boundaries are publicly verifiable. Borderline cases can be independently confirmed using the polygon data (excluding the hatched SIGN overlay, which is not a probability rating) and the city's listed coordinates. The point-in-polygon test is performed on unprojected WGS84 (EPSG:4326) coordinates, which is the native coordinate system of the SPC GeoJSON data.
Resolution is based on the scheduled 01:00 UTC Day 1 Convective Outlook update issued on the following UTC calendar day. The SPC Day 1 outlook covers a 24-hour period from 12:00 UTC to 12:00 UTC the following day. Subsequent revisions published after that scheduled update will not be considered. If the SPC outlook is not published or is unavailable, the market remains open until data is available.
The resolution source for this market is the NOAA Storm Prediction Center at spc.noaa.gov.
This market uses coordinates 41.8781, -87.6298 for Chicago, IL.
Resolution Source
https://www.spc.noaa.gov/products/outlook/day1otlk.htmlResolver
0x65070BE91...**SPC Day 1 convective outlooks issued September 4, 2026, placed a Slight Risk of severe thunderstorms across the southern Great Lakes into the mid/upper Ohio Valley and mid-Atlantic, driven by a frontal zone and northwesterly flow aloft.** Tornado probabilities remained low, with a 2% contour covering parts of central Ohio and adjacent Indiana, while broader areas saw 5–15% damaging wind and 5% hail risks. Official NWS surveys confirmed tornadoes the prior day (September 3) in Detroit (peak winds ~115 mph) and Seneca County, New York, but no comparable confirmed events were highlighted for September 4 itself amid ongoing clusters favoring straight-line winds. Model consensus emphasized organized thunderstorm clusters capable of gusts to 70 mph overnight, with limited rotation potential due to modest low-level shear. Traders monitoring resolution criteria—such as any SPC-defined tornado watch or verified reports within city boundaries—would next watch updated Day 2 outlooks and real-time mesoscale discussions from the Storm Prediction Center for shifts in instability or shear.
Experimental AI-generated summary referencing Polymarket data. This is not trading advice and plays no role in how this market resolves. · Updated

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