Minnesota summers aren’t getting hotter. But they are getting more humid.
Thanks to a heat wave set to last through Sunday evening, the state is in for both this weekend. The heat index — or how hot it feels when you add in humidity — could reach as high as 110 degrees in parts of southern Minnesota, according to the National Weather Service.
That’s a rare event for this early in the summer, said Kenneth Blumenfeld, senior climatologist for the Minnesota Department of Natural Resources. Since 1970, Minnesota has only experienced a total of 24 June days when the heat index clocked in at 100 degrees Fahrenheit or higher, he said.
Yet even as the global average temperature continues to climb, data shows that Minnesota summers haven’t gotten hotter, just more balmy, Blumenfeld said.
“We see increases in the frequency of humid days, days where the dew-point temperature gets to 70 degrees or higher,” he said. “But what we’re really seeing are increases in the intensity of the humidity, so how high that dew point gets, or how high the heat index gets.”
It’s one of the ways climate change has manifested during the summer, which so far has been the season least affected in the state by rising global temperatures. By contrast, Minnesota winters have warmed significantly, data shows, causing more midwinter melts and fewer days with frozen lake ice and snow on the ground.
Hotter overall temperatures allow the air to hold more moisture, Blumenfeld said. It also means more water is evaporating from the ocean and being dumped over land, including in Minnesota, which receives air from the Gulf of Mexico.
“Minnesota is in an area where annual precipitation, on average, has increased over the past few decades, and the extremes of precipitation … have also increased on average,” Blumenfeld said.