July 1936 holds our records for extreme heat

Published: Jul. 13, 2020 at 2:07 PM CDT|Updated: Jul. 13, 2020 at 2:11 PM CDT
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CEDAR RAPIDS, Iowa (KCRG) - Parts of the southwestern United States have been baking under heat that has been around record highs. Meanwhile, our temperatures have been reasonably close to normal for July. When it comes to all-time heat records, how does our area look?

Cedar Rapids’ hottest temperature was 110 degrees, set on July 6, 1910. The blistering heat wave in 1936 holds the next slots, though: 109 degrees on July 14 and 108 degrees on July 13, July 26, August 3, and August 18. In July, there was a string of 13 straight days with highs in the 100s.

Dubuque’s hottest temperature on record is also 110 degrees, set on July 14, 1936. The next five hottest days were also in 1936. It was 107 degrees on July 11, July 13, July 26, and August 18, and 106 degrees on July 12. In the 13-day stretch of the most extreme heat, only one day didn’t get to 100: July 16 at 98 degrees.

Iowa City’s records at the airport peaked at 105 degrees on July 7, 23, and 25 in 2012. Not surprisingly, the long-term climate site there had its hottest temperatures in 1936. July 14 registered a high of 109 degrees, and three other days that year were at 108 degrees (July 15, July 26, and August 18). Like Cedar Rapids, there were 13 straight days with a high above 100 degrees.

Waterloo is the champion of heat, topping out at 112 degrees on July 13 and 14, 1936. Those were part of a 13-day streak above 100 degrees. They hit 110 degrees on July 12 and August 18 that year, too.

Officially, Iowa’s all-time record high was set two years earlier when Keokuk hit 118 degrees on July 20, 1934. However, there’s doubt about the accuracy of that reading, and the state’s true all-time record probably happened on July 25, 1936.

The average monthly high in Iowa in July 1936 was in the upper 90s to around 100 degrees.
The average monthly high in Iowa in July 1936 was in the upper 90s to around 100 degrees.(Midwest Regional Climate Center)

If you’re wondering why our region’s hottest weather didn’t happen more recently – and that global warming must therefore be false – remember two things. First, what happens in Iowa or even the United States doesn’t necessarily represent what’s happening to the planet as a whole. Second, how we use our land has changed drastically in the past decades and that’s caused a measured decrease in extreme heat here. Millions of acres of corn are planted each year that weren’t there in the past, and the incredible amounts of moisture they put out makes it harder for the air to get as hot. If you want to know what happens when crops dry and wither, look no further than 1988 and 2012. On the flip side, overnight lows have warmed because of the consistently wetter air.

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