How Minnesota’s Early Fall ‘Micro-Season’ Creates Picture-Perfect Weather – WCCO
MINNEAPOLIS (WCCO) – It is a time of year when there is often little or no significant humidity, no strong winds and no rain to destroy our plans. Some might just call it fall, but it’s something more specific than the third season of the year.
“Moved from California thinking spring would be my favorite time of year and no, I love fall,” Chris Streiff Oji said as she strolled around White Bear Lake with her husband.
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Her sentiment is hard to dispute as people seize the last moments of summer at the start of fall.
“If we could have it like this all year round, that would be great,” she said.
Unfortunately for her, these awesome conditions last barely two weeks, and they are happening right now. Dr. Kenneth Blumenfeld, senior climatologist at the Minnesota Department of Natural Resources (MDNR), described this time of year as a micro-season.
“It’s part of what makes the fall so spectacular,” said Blumenfeld. “And that is to have clear skies, good weather and generally nice and pleasant conditions in late September and early October.”
MDNR tracks which time of year has, on average, the highest probability of clear skies. The peak is the current pocket of early fall, six times more likely than June. The most marked peak in probability occurs specifically between September 27 and October 3. The end of January comes in second, but clear skies at this time of year often indicate a cold, subzero day.
“Air pressure tends to be a bit higher this time of year,” he said. “This means that the air pushes more down on the earth and it prevents the formation of clouds.”
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The micro-season is felt by people living in the Upper Midwest, from Canada to Missouri. Scientists at the University of Minnesota discovered the weather pattern in the 1970s. And while cloudy, rainy, and cool days can occur during this brief period, the trend has continued over the decades. Dr Blumenfeld said the chance of clear skies is only around 15%, but that’s higher than at any other time of year.
“I think it’s definitely something that people maybe subconsciously notice,” he said.
While the percentage is low, it might be enough to convince people to plan some outdoor projects in early fall in the hopes of getting a perfect day.
“But you had better have a Plan B because if you don’t get that spectacular weather, which is more common now than at any other time of the year, you might get something that you will remember. a different way, ”he said.
Another unique weather trend during this same stretch is a wider range of high and low temperatures each day. The range generally peaks in summer, before decreasing as winter approaches. But in late September and early October, the clear skies allow for cooler nights and warmer days. According to the MDNR, the average daily temperature range is 11.6 degrees from September 20 to 28. It jumps 20.8 degrees from September 29 to October 4.
“We are entering a pattern where we are starting to lose moisture. All the vegetation starts to dry out and this tends to stop the rainy season. And so the air dries up a bit. It makes it easier to change the temperature, ”said Blumenfeld.
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What will it take to end this wonderful period of time? Typically, humidity returns when the temperature drops later in October. Clouds form more often, creating a dark chill that will cause people to search for sweatshirts and blankets as they head for a fall bonfire.