September warmth has pushed fall colors about 2 weeks later since 1970

It’s another September summer day in Minnesota. And it’s not your imagination that September feels warmer than it used to.

Climate records show September is now much warmer than it used to be 50 years ago on average.

I spoke Wednesday with Pete Boulay of the Minnesota State Climatology Office about the trend of warmer fall seasons in Minnesota. One number made me do a double take: Septembers in Minnesota are now about 6 degrees warmer on average than in 1970.

Six degrees is a seismic trend when it comes to a monthly average temperature. September has now basically turned into a fourth month of summer for Minnesota in the past half century.

Overall, fall temperatures in the Twin Cities have warmed more than 5 degrees since 1970.

Minnesota is one of the fastest warming areas of the country in the fall season.

Fall color peak trending 2 weeks later

Pete highlights another trend that’s changing dramatically as our Minnesota climate warms. He told me Minnesota phenology expert Jim Gilbert reports that Minnesota’s annual fall color peak has trended about two weeks later since the 1960s.

That trend is also occurring nationally. Here’s one fall color forecast for 2025.

The trend of later fall color changes is bring reflected in this balmy September as I wrote about this week. Temperatures have been running 5 to more than 10 degrees warmer than normal in Minnesota over the past seven days.

Our latest September heat wave brings highs in the 80s to much of southern and western Minnesota into next week to close out the month.

So expect fall color peak in your area to be about one to two weeks later than normal once again due to our September climate changes in Minnesota.

You can hear more details on our warmer fall season in Minnesota on my latest Climate Cast episode airing on MPR News stations Thursday afternoon during All Things Considered.