Days Over 100 degrees F Are Not Increasing in Iowa

In a story at Radio Iowa, the climate alarmism is being raised another notch as "Iowa farmers warned to prep for more wild weather":

A new report on climate change offers a warning for farmers across Iowa and the Midwest to prepare for significant weather-related challenges in the years ahead.

Climate scientist Don Wilhite says average temperatures will continue rising in our region with a substantial increase in high-temperature stress days over 100 degrees.

We do need to have a discussion about the number of days over 100 degrees (aka, >100º F) in Iowa.  Here are the trends in number of days per year >100º F since records began in the 1800s for Iowa's four climate sub-regions from the NOAA National Weather Service database:

The data speaks for itself.  In recent decades, the state has seen nothing close to the number of days above 100º F that it experienced during the 1930s.  The Waterloo area had 15 days >100º F in 1934 and a record 19 in 1936.  It has had only 25 such days since 1936.  In other words, the region had 40 percent more days above 100º F in the three-year period from 1934 to 1936 than it has had in the 80 years since.

The Des Moines area had 22 days above 100º F in 1934 alone.  The last 30 years inclusive have had 23.  The Sioux City region had 28 days >100º F in the single year of 1936.  The past three decades have brought only 25.  The Dubuque area had 13 days >100º F in 1936.  In the entire period since 1936, there have been a grand total of three days >100º F (one of which came in 1940, so that is just two days since 1940 – one in 1988 and one in 2012).

Not only are there no significant trends toward an increasing number of days above 100º F since records began, or since 1970, or over the last three decades, but the correlations since records began and during the past 30 years are negative – toward fewer of these extreme heat days, not more.

And here is Iowa's summertime average maximum temperature since records began in 1895.  The statistically significant trend is negative, towards cooling.

No evidence of a significant increasing trend since 1970 or 1985, either.

As for average temperatures continuing to rise: there is no significant trend in Iowa's average temperature over the past century, or over the last 30 years.