Warm Summer Nights Increasing in Maine Amid Climate Concerns

PORTLAND, Maine — As summer approaches, the nights in Maine are getting warmer, a trend fueled by climate change. In the first half of the 2020s, the number of nights with temperatures exceeding 70 degrees is surpassing the total from the 2010s.

The Climate Shift Index (CSI) is a key tool used by scientists to measure the impact of human-driven climate change on temperatures. For example, a CSI of 2 indicates that a specific temperature is now twice as likely to happen due to global warming.

While daytime temperatures are rising, nighttime temperatures are increasing even faster in many regions. In parts of the Southwestern U.S., areas have recorded more than 60 summer nights each year that are now at least twice as likely to occur because of climate change.

Maine is experiencing similar changes. Since 1970, average summer night temperatures have climbed nearly 4 degrees Fahrenheit. Currently, there are more than 30 nights per year with temperatures classified as above normal, also significantly influenced by climate change.

To illustrate this shift, an “uncomfortably warm night” in Maine is defined as a night where temperatures do not drop below 70 degrees. In the 1970s through the 1990s, Portland experienced around 8 of these nights per decade. The number has now skyrocketed, reflecting a substantial increase.

This rise in warm nights has real implications for public health, sleep quality, and energy consumption. With the ongoing effects of climate change, warm summer nights are becoming commonplace in Maine.