‘Excessive Heat Watch’ Issued for Iowa

The National Weather Service in Des Moines has issued an "Excessive Heat Watch" for more than half the state of Iowa on Wednesday, July 28.

Heat indices in the watch area are expected to reach as high as 102-110*.

Highs will be in the lower 90s on Monday, the middle 90s Tuesday, and near 100* on Wednesday.

As of Sunday, July 25, Cedar Rapids saw 11 days reach at least 90* in 2020. So far this year (through July 25th) the city has seen 10 days reach that level.

Waterloo has seen a total of 20 days reach at least 90*, including 100* on June 17. In 2020, Waterloo had 29 days to reach at least 90*.

Between 1986-2020, extreme heat caused the death of 4308 people.

The Heat Index is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature. Our bodies try to keep us cool by losing water through the skin and sweat glands. But when the humidity is too high, our sweat won’t evaporate. The higher the humidity, the harder it is for the body to sweat and cool itself down.

According to Jim Lee at the National Weather Service, the highest observed heat index in Cedar Rapids occurred during the 1995 heatwave on July 13. The air temperature was 100° and with a dew point of 85°, the heat index of 131° (old scale).

As for Waterloo, Cory Martin from the National Weather Service in Des Moines says the highest heat index was 120° on July 12, 1995. That was from a temp of 97° and a dewpoint of 80°.

On average, Waterloo & Cedar Rapids will spend over 60 hours/year with a Heat Index at/over 100*. So far this year, Waterloo has spent ONE hour with a heat index of 100*. Cedar Rapids has yet to see a heat index over 98* this summer. (as of 7/22)

Per the National Weather Service:

An Excessive Heat Watch is issued when conditions are favorable for an excessive heat event in the next 12 to 48 hours.

An Excessive Heat Warning/Advisory is issued when an excessive heat event is expected in the next 36 hours.