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Late August heat wave smashes several records in central Iowa

Des Moines shattered three separate records in a 24-hour period from Wednesday morning to Thursday morning.

DES MOINES, Iowa — The recent heat wave will have a prominent spot in the August weather records line-up for Des Moines and other areas of central Iowa.

On Wednesday, Aug. 23 alone, Des Moines shattered two records: the warmest morning low temperature in recorded history, and the hottest afternoon high temperature in recorded history. 

Wednesday morning's low came in at 80°, breaking the previous Aug. 23 low temperature record of 78°, set back in 1878. 

The high temperature in Des Moines reached 100° on Wednesday afternoon, breaking the previous Aug. 23 high temperature record of 99°, set back in 1975.

For reference, Des Moines hadn't recorded a triple digit air temperature since June 2021. 

RECORDS BROKEN! | Yesterday was one for the books. We broke heat records in the morning AND the afternoon. This...

Posted by Meteorologist Brandon Lawrence on Thursday, August 24, 2023

Des Moines just missed out on triple digits on Thursday with a high of 99.  If it would have been one degree warmer it would have been the first back-to-back days of triple digit high temperatures since July 2017 - more than six years ago! 

No record was set either.  Thursday's record high of 104 occurred in 1936, during the Dust Bowl. 

Unofficially, Des Moines did break one more record, however. Thursday morning's low temperature only fell to 79°, which beats the previous record of 76°, set back in 2021.

Here's a closer look at the official high and low temperatures for Des Moines since this heat wave began last weekend (an asterisk denotes a new record): 

High temperatures since Aug. 19, 2023

  • Saturday, Aug. 19 - 92°
  • Sunday, Aug. 20 - 94°
  • Monday, Aug. 21- 92°
  • Tuesday, Aug. 22 - 96°
  • Wednesday, Aug. 23 - 100°*
  • Thursday, Aug. 24 - 99°

Low temperatures since Aug. 19, 2023 

  • Saturday, Aug. 19 - 66°
  • Sunday, Aug. 20 - 78°*
  • Monday, Aug. 21- 76°
  • Tuesday, Aug. 22 - 75°
  • Wednesday, Aug. 23 - 80°*
  • Thursday, Aug. 24 - 79°*

This late August heat wave is exceptional for a number of reasons: 

  • Des Moines has hit 90° or above for five days in a row, and will make it seven by the time the work week has finished. This is the longest stretch of 90°+ temperatures this summer. Previously, Des Moines had only reported a three-day stretch of 90°+ temperatures, from July 26-28. 
  • Des Moines recorded a heat index of 115° on Wednesday afternoon, tying 5th place for the highest index readings ever recorded in the city. The highest heat index on record is 122°, which occurred in 1936. Additionally, the heat index of 115° was the highest on record ever in the month of August. 
  • It is late in the summer, and days are getting shorter. The average temperature for Des Moines at this time of year is in the low 80s. 
Credit: WOI

Thursday marked the 6th consecutive day of 100°+ heat indices.

Peak Heat Indices since Aug. 19, 2023

  • Saturday, Aug. 19 - 104°
  • Sunday, Aug. 20 - 106°
  • Monday, Aug. 21- 106°
  • Tuesday, Aug. 22 - 113°
  • Wednesday, Aug. 23 - 115°
  • Thursday, Aug. 24 - 112°

Friday is also forecast to make it above 100° for a heat index.  7 Days consecutive with a heat index of 100 or more has only happened five other times in history.  Only two were longer.  A stretch of 9 days in late July/early August of 1955 and the longest of 10 days in the same timeframe of 1987!  The most recent was a 7 day string in early July 2012.

Credit: Chris Kuball
Top stretches of consecutive 100° Heat Index Days

The final three days have all had a heat index above 110°.  This has also only happened two other times in history, July of 2011 and August 1983.  The latter occurred in one of the hottest Iowa State Fairs ever.

By this weekend, temperatures are set to retreat to the 80s, but it is likely there are still a few more 90s in our future. 

In the last five years, the final 90° of the season in Des Moines always occurred in September. 

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