Excessive Heat — Monona, Iowa

2023-08-21 to 2023-08-24 · Monona, Iowa

Event narrative

For 4 days beginning on August 21, the high temperature in Mapleton reached at least 95. The highest observed temperature was 99, occurring on both August 22 and August 23. Dew point temperatures in the area were in the mid to upper 70s which yielded a heat index of at least 105 all 4 days.

Wider weather episode

An Excessive Heat Warning was in effect for portions of the forecast area for 7 days as a heat wave dominated the area. This was the longest duration Excessive Heat Warning that the Omaha office has issued. A total of 10 temperature records at Omaha, Lincoln, and Norfolk were tied or broken as the air temperature routinely topped 100 and overnight low temperatures largely remained above 75. High dew points led to heat indices that routinely topped 110.

The heat wave began on August 19 as a mid-level ridge moved over the central CONUS. Temperatures in southwest Iowa ranged from the mid 90s and reached 100 at the Council Bluffs airport. Heat indices topped 120 for several days as dewpoint temperatures were near 80. A cold front moved into the area on August 20, but only brought a brief relief. Overnight low temperatures the morning of August 20 largely remained above 75 degrees. On August 21, afternoon highs returned to the 90s and heat indices easily topped 110.

Source: NOAA Storm Events Database, event_id 1130425. Narrative written by the NWS forecast office that issued the report.