Maine summers heat up: Extreme temperature days rise over the past 55 years

PORTLAND (WGME)– Summer days have been getting warmer in Maine over the last 55 years, and this has led to an increase in the hottest days of summer with more extreme heat days.

An extreme heat day for Maine is any day with the temperature reaches 77 degrees or higher with a climate shift index of level 2 or higher.

The climate shift index rates every day on how likely the temperature would be with and without climate change.

For example, on June 20, 2024, Portland saw a high temperature of 94 degrees.

This hot day had a climate shift index of 3- meaning that the hot temperatures we saw were made 3 times for likely due to climate change.

Much of the United States has seen an increase in the number of extreme heat days in the summer with the largest increase over the south central US in places like Texas.

Maine and New England have also seen an increase in extreme heat days.

For Portland in the 2020s so far, we have seen about 10 more days on average with extreme heat that was made at least twice as likely due to climate change.

The increase in extreme heat days has been a little less notable, but on average in the 2020s we see about 5 more days with extreme heat that was made at least twice as likely due to climate change.

With a warmer than normal summer likely, we may end up seeing more of these climate shifted days in Maine this summer.