George Isobar talks about July weather 2011.08.03

Written by David Green.

By DAVID GREEN

Hot enough for you?

Last month was definitely on the toasty side—a record warm July in Detroit—but the suffering was even worse a few decades earlier.

The Great Heat Wave of 1936 produced what still stands as the hottest summer on record in the United States.

The past July was a hot one, with a high temperature of 103°July 21 and a 100° reading July 2. Of July’s 31 days, temperatures were in the 90s and above on 23 of them. The average for the month was 5.8° higher than average.

And what about 1936? There were 19 days in the 90s and above—way above. The Observer from that year tells the tale of torturous temperatures.

On July 6, the mercury pushed to 97°, but Mother Nature was just warming up. The next day it rose to 107°. For seven days in a row, the high temperature was 103° or greater. 

Previous to 1930, reported the Observer, the record high in Morenci was 108°, but that was broken July 12 at 109° and that same temperature was recorded one more time July 14.

It was a seven-day inferno, wrote publisher F. Russell Green. The string of 100-plus days ended, the temperature cooled to 97°, followed by nine more days in the 90s.

That wasn’t the end of it. There were four more days in the 100s later in August.

It was a year of extremes, wrote Christopher Burt in his weather blog, because the hottest summer on record was preceded by one of the coldest. For example, a town in North Dakota recorded a temperature of -60° in February 1936. In July, a town 110 miles away recorded a high temperature of 121.

Several states to the south and west had already set monthly high records in June, but by July the heat dome was locked into place over the Great Plains. Seventeen states broke or equaled their all-time maximum temperature that summer, including Michigan with a high temperature in Mio of 112°.

“It may have been a lot hotter in 1936, but it also got cooler at night,” said Morenci climate observer George Isobar, after looking through the Observer archives. “Four of 100-plus days were followed by nights in the 70s, but so many other days that month started off with lows in the 50s and even two in the 40s. There were some cool nights that we didn’t get last month.”

There were 11 nights here last month when the temperature stayed in the 70s overnight, and just one where it dipped into the 50s. The reason for the difference is moisture—or the lack of it. There was dryer weather in the summer of 1936, said meteorologist Danny Costello from the National Weather Service office in White Lake, Mich., and that allowed the air to cool.

“Dry air heats up and cools off quicker than humid air,” he said. “This year we have a humid airmass.”

Morenci was fortunate with those night-time lows in 1936 because that wasn’t the case everywhere. According to Burt’s article, Bismarck, N.D., recorded a night-time low of 83° on July 11. In Milwaukee, a string of five days never got cooler than 80°.

The most amazing statistic that Burt discovered came from Lincoln, Neb. The overnight low was a miserable 91°, followed by an all-time record high of 115° the next day, July 25.

“We had our share of suffering last month,” Isobar said, “but think of all those 100° days without air conditioning. I’ll take our heat to that experienced in 1936 any year.”

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