Aug 31st - Sept 5th, 2026 Heatwave

Overview

Fast Facts:

A prolonged heat wave occurred August 31st through September 5th across much of the middle and lower Mississippi river valley and the central Plains.
Very warm temperatures combined with dew points above 70 degrees for several days, made for dangerous heat index values between 100° to 115° each day. Little relief was provided at night, with temperatures remaining the low to mid 70s. Record warm lows occurred at Dubuque (9/3 + 9/4) and Moline (9/4).
There were many consecutive hours (70+) of dew points greater than or equal to 70° at all climate sites during this period which allowed for the heat-related illnesses from the cumulative effects.
Dangerous heat was observed during the University of Iowa Hawkeye football game in Iowa City Saturday Sept 5th, with one confirmed fatality.

NWS Headlines: 10 AM Thursday Sept 3rd

NWS Headlines: 10 AM Thursday Sept 5th

Temperatures & Heat Indices
Dew Point
Additional

Temperatures & Heat Indices


Summary Infographic


Monday, August 31st High Temperatures	Tuesday, September 1st High Temperatures	Wednesday, September 2nd High Temperatures

Thursday, September 3rd High Temperatures	Friday, September 4th High Temperatures	Saturday, September 5th High Temperatures

...Highest Heat Index Readings Between Aug 31st and Sept 1st...

Observations are collected from a variety of sources with varying
equipment and exposures. We thank all volunteer weather observers 
for their dedication. Not all data listed are considered official.

Location                     Heat Idx. Time/Date       Provider             
Freeport Arpt                112 F     0415 PM 09/01   AWOS                 
Macomb Arpt                  109 F     0255 PM 09/01   AWOS                 
Washington Arpt              108 F     0655 PM 08/31   AWOS                 
Cedar River Tnc Swamp        108 F     0346 PM 09/01   RAWS                 
Shimek State Forest          107 F     0507 PM 08/31   RAWS                 
Fairfield Arpt               107 F     0355 PM 09/01   AWOS                 
Clinton Arpt                 106 F     0256 PM 09/01   AWOS                 
Muscatine Arpt               106 F     0435 PM 09/01   AWOS                 
Sterling/Rock Falls Arpt     106 F     0156 PM 09/01   AWOS                 
Burlington Arpt              105 F     0123 PM 09/01   ASOS                 
Independence Arpt            105 F     0315 PM 09/01   AWOS                 
Vinton Arpt                  105 F     0215 PM 09/01   AWOS                 
Fort Madison Arpt            104 F     0335 PM 09/01   AWOS                 
Quad City Intl Arpt          104 F     0352 PM 09/01   ASOS                 
Dubuque Arpt                 103 F     0353 PM 09/01   ASOS                 
Iowa City Arpt               103 F     0352 PM 09/01   ASOS                 
Cedar Rapids Arpt            102 F     0352 PM 09/01   ASOS                 
Davenport Arpt               102 F     0252 PM 09/01   ASOS                 
Mount Pleasant Arpt          101 F     0355 PM 09/01   AWOS

...Highest Heat Index Reports Sept 3rd...

Location                     Heat Idx. Time/Date       Provider                                                                 
Macomb Arpt                  111 F     0555 PM 09/03   AWOS                                         
Washington Arpt              107 F     0455 PM 09/03   AWOS                 
Burlington Arpt              107 F     0253 PM 09/03   ASOS                 
Fairfield Arpt               107 F     0535 PM 09/03   AWOS                 
Fort Madison Arpt            107 F     0355 PM 09/03   AWOS                 
Muscatine Arpt               107 F     0615 PM 09/03   AWOS                               
Clinton Arpt                 106 F     0356 PM 09/03   AWOS                 
Sterling/Rock Falls Arpt     106 F     0356 PM 09/03   AWOS                                             
Iowa City Arpt               105 F     0252 PM 09/03   ASOS                 
Quad City Intl Arpt          105 F     0452 PM 09/03   ASOS                 
Mount Pleasant Arpt          105 F     0435 PM 09/03   AWOS                                            
Freeport Arpt                104 F     0555 PM 09/03   AWOS                                                
Cedar Rapids Arpt            103 F     0252 PM 09/03   ASOS                            
Dubuque Arpt                 102 F     0353 PM 09/03   ASOS                 
Davenport Arpt               102 F     0452 PM 09/03   ASOS                 
Vinton Arpt                  102 F     0555 PM 09/03   AWOS

Dew Point

The dew point is the temperature the air needs to be cooled to in order to achieve a relative humidity (RH) of 100%.

The higher the dew point rises, the greater the amount of moisture in the air. This directly affects how "comfortable" it will feel outside. Many times, relative humidity can be misleading. For example, a temperature of 55 and a dew point of 55 will give you a relative humidity of 100%, but a temperature of 80 and a dew point of 60 produces a relative humidity of 50%. It would feel much more "humid" on the 80 degree day with 50% relative humidity than on the 30 degree day with a 100% relative humidity. This is because of the higher dew point.

So if you want a real judge of just how "dry" or "humid" it will feel outside, look at the dew point instead of the RH. The higher the dew point, the muggier it will feel.

More on Dew Points Including Peak Dew Points Observed Aug 31st - Sept 5th, 2026

High Dew Point Duration Facts:

Additional Information

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