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This summer in the Twin Cities has been the longest stretch of hot weather on record

The Twin Cities had their longest streak of days on record that reached 70 degrees or more this summer.

The 118-day period, from May 27 to September 21, beat the previous 107-day span set in 2018, according to the National Weather Service office in Chanhassen.

The heat, as well as dry conditions throughout the summer, could also dull fall colors. The temperature sequence may be less noticeable than the hot summer days, but it is part of a larger pattern.

“We are extending summer into September longer than before,” said Pete Boulay, a climatologist with the Minnesota Department of Natural Resources.

Climate change is driving up temperatures across the globe, though so far that signal has shown up in Minnesota with warmer, shorter winters.

This will not always be the case. According to the Fourth National Climate Assessment, “warm season temperatures are projected to rise more in the Midwest than in any other region of the United States.”

In the Twin Cities, most of those long periods of highs above 70 have occurred in the past 20 years, said weather service meteorologist Jacob Beitlich.

Besides the unusually persistent heat, this year is also notable for the drought conditions that have persisted around the Twin Cities. The area is still in the severe drought category, according to the US Drought Monitor.

So far, 2022 is on track to be the fourth driest summer, counting records for rainfall between June 1 and September 30.

Significant rains are unlikely to arrive until the end of the month. A single computer model shows about five hundredths of an inch falling in the next few days, which Beitlich called an almost “comical” amount.

So, in addition to contributing to an overall dry summer, it’s likely to be the driest September since weather records began in the Twin Cities in 1871. That would break a dry September record set in 1882, Boulay said.

Combined heat and dryness can also affect fall color.

Val Cervenka, coordinator of the DNR’s forest health program, said the leaves are starting to change color due to the combination of cooler temperatures and shorter days. Persistent heat as daylight dwindles can blur the colors of emerging leaves.

Drought is also a well-known factor in fall color, Cervenka said. If the trees don’t get enough water, their leaves may look duller or simply wrinkle and brown, rather than displaying brilliant reds and yellows.

In particular, the anthocyanins that create a scarlet show in some hardwoods aren’t produced without cold nights, she said.

“As we stay warmer, the color just doesn’t happen,” Cervenka said. “If a tree also breathes more because it’s hot and water evaporates faster from the leaves, that’s going to have an effect.”

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