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Fall in Maine is arriving later, getting warmer

Fall is in the air, though we have a couple weeks left of meteorological summer. It's a transitional time not just for our wardrobes, schedules and outdoor activities, but for the climate. 

We know that the overall warming trend of human-caused climate change is reshaping and shifting the timing of our seasons — all anchored around the fastest-warming season, winter.

The shortening cold season, with fewer days of snow cover, is reflected in later falls and earlier springs — affecting plants and animals, the water cycle, outdoor recreation, energy use, infrastructure and more. 

Here's some evidence: The state climatologist's office reports Maine has seen above-normal temperatures in September (where "normal" is the 21st-century baseline) almost every year since the late 1990s, with a peak at 6.9 degrees Fahrenheit above normal for September 2015. 

Last fall was one for the record books — September 2023 was 5.9 degrees above normal (second only to 6.9 degrees in 2015), and October 2023 was 7.3 degrees above normal (behind 7.7 degrees in 2017). We also wrote in this newsletter a couple years ago about record November warmth. Remember that week around Election Day in 2022 when the weather was much like it has been in Maine this week? 

Federal data shows that the fall season has warmed the most in Maine after winter, unlike in many other states, where spring or summer are second in line. 

National data analyzed by the nonprofit Climate Central shows that the average fall temperature in parts of Maine has increased by about 3 to 5 degrees since 1970, more than the national average. 

The analysis found fall warming in 97% of the 242 locations they studied, with increases above 3 degrees in a third of those places. The fall warming signal is strongest in the Southwest, and parts of Maine are seeing a comparable level of change. 

Climate Central says that Portland, Bangor and Presque Isle are now seeing at least two to three more weeks' worth of above-normal temperatures each fall as they did about 50 years ago. ("Normal" here is the 1991-2020 baseline.)

A few degrees of warming might not seem like much. But ecosystems — including their human inhabitants — have evolved to respond in complex ways to minute changes in temperature, light and other factors. A small shift in climate can have big ripple effects, and we're only at the start of a long-term trend. 

Among the impacts for people: more energy demand for cooling, including at the start of the school year in buildings that may be ill-equipped to provide it; a longer and more intense allergy season; and more smoke from deadlier wildfires drifting cross-country in hotter weather, increasing respiratory risks. 

Warmer falls, winters and springs are also a boon for disease-carrying ticks, which can emerge earlier and feed longer in milder temperatures. 

One climate impact that's less clear is on fall foliage. The factors that affect its timing and color are complex. Some aspects of warming cause leaves to drop later, but droughts can have the opposite effect. 

Scientists know more about how climate change is affecting signs of spring — leaf-out, bird migration and more. More research is still to come on the autumn side of the calendar, to determine not just how much this season is warming, but what that warming will mean for nature and the built environment. 

ICYMI from The Monitor

Don't miss the latest installment in Kate Cough's series "Sinking in Saltwater," on a dam removal debate in Addison that raises the fascinating question of what makes an ecosystem "natural." Joyce Kryszak is covering the winter outlook for Machias's eroding dike. And I have a new story about the lawsuit over Maine's failure to adopt stronger electric vehicle sales targets as part of its statutory climate targets. 

Vermont Public's Abagael Giles writes about what years of devastating floods mean for the Green Mountain State's reputation as a "climate haven." 

And I'm obsessed with this recent story by Louisiana Illuminator's Wesley Muller, comparing the responses to a recent offshore wind turbine failure in New England and an oil spill in Louisiana. See also: This excellent, comprehensive piece on the Vineyard Wind incident from the Rhode Island Current. 

While The Maine Monitor does not place its content behind paywalls, some newsrooms we link to in this newsletter may. 

Brunswick council passes resolution calling for state action to clean up firefighting foam | Maine Morning Star

PFAS spill raises questions about older fire systems found in U.S. airport hangars | NPR/Maine Public

'I feel helpless:' Brunswick residents concerned as toxic foam cleanup continues | WGME

Maine cracks down on multiple businesses for contaminating the environment | Portland Press Herald

Pipeline talks could send Maine natural gas prices soaring | Bangor Daily News

Maine to ban utilities from charging ratepayers for lobbying | Portland Press Herald

Mainers could see significant savings on energy bills in the next two decades, report finds | Maine Public

National Weather Service revises cold weather alert system starting October | WGME

China residents to vote on high-voltage power line ban after citizens’ petition | Portland Press Herald

Study takes on Maine’s growing piles of trash | Bangor Daily News

Cruise ships back on the ballot for Bar Harbor voters this November | Maine Public

Some cry 'fowl' after loon moved from Little Sebago Lake to Massachusetts | Portland Press Herald

Maine's national parks added $750 million to the economy last year | Maine Public

There’s more to Aroostook farms than potatoes | The County

3 weeks inside Thomas Dambo's world of trolls | Maine Public

Know of a story that we should be digging into? Send it to our newsroom. 

The Maine Monitor is a publication of the Maine Center for Public Interest Reporting, an independent and nonpartisan nonprofit news organization that produces investigative journalism. We believe news is a public good and keep our news free to access. We have no paywall and do not charge for our newsletters. If you value the reporting we do for Maine, please consider making a donation! We cannot do this reporting without your support.