A new climate report from the Union of Concerned Scientists predicts that Maine could see more than a 10-fold increase in the number of 90-plus degree days by midcentury and up to 11 days by century’s end when temperatures top 100 degrees.

The report and an accompanying scientific paper, published Tuesday by the scientific advocacy organization, projects that “extreme heat” events will increase dramatically in nearly every corner of the United States with a few exceptions in mountainous regions.

LIfeguard Bobby Slattery takes a drink of water on Wednesday at Old Orchard Beach during another day of hot weather. Ben McCanna/Portland Press Herald

The number of days when the heat index – a “feels like” measure combining temperature and humidity – crests 100 degrees or 105 degrees Fahrenheit is projected to double and triple, respectively, unless emissions of climate-altering gases are curtailed to limit warming to 2 degrees Celsius or 3.6 degrees Fahrenheit. An increase in such extreme heat events will have an impact on human health, agriculture, the economy and population-migration trends.

The heat picture painted for Maine and the rest of New England is, not surprisingly, less intense than that for Southern and Midwestern states. But the analysis, which is based on historic temperature data and climate models, suggests New Englanders will have to adjust to more frequent occurrences of heat events more typical today of places in the Deep South.

The “extreme heat” analysis is just the latest report predicting major impacts on Maine’s commercial fisheries as well as other sectors of Maine’s tourism, agricultural and forestry economies.

The Union of Concerned Scientists report estimates that Maine could experience 14 days with a heat index of 90 degrees Fahrenheit or above by the “midcentury” period that extends from 2036 to 2065, compared to just one day on average currently.


By the last three decades of this century, that number could jump to 36 days per year, but would be limited to nine days if temperature rise is held to 2 degrees Celsius.

“This is certainly a national story and the most dangerous changes are in the southern parts of the country … however, those changes will reverberate outside of that region and will affect people in New England and Maine,” said Erika Spanger-Siegfried, lead climate analyst for the Union of Concerned Scientists.

Cumberland County, for instance, could see the number of days with a heat index above 90 degrees increase from three, on average, to between 17 and 25, depending on the level of efforts to reduce emissions.

In Portland, the number of 90-plus degree days could jump from two to 20 by midcentury and to as many as 48 days per year by the latter portion of the century. Maine’s two other largest cities, Bangor and Lewiston, could see even larger jumps in the number of extreme heat days, with all three potentially experiencing several weeks of 100-plus degree days by the latter part of the century if no action is taken.

“That’s a pretty significant change and that’s on par with what places like Montgomery, Alabama, have experienced historically … or places like Savannah, Georgia, and Las Vegas, Nevada,” Spanger-Siegfried said.

Maine’s southern New England neighbors would be similarly affected. Massachusetts, for instance, is projected to see 33 days of 90-plus degree heat index days by midcentury and 62 days by century’s end, compared to seven per year now.


The Union of Concerned Scientists is a national nonprofit employing several hundred scientists who conduct research and advocate on policy, particularly on issues such as climate change, environmental safety and sustainability. The vast majority of the group’s funding comes from member contributions or foundations.

The organization’s report comes at a time of increasing scientific alarm over climate change and frustration with the Trump administration’s inaction on the issue. After withdrawing the United States from the Paris Climate Accord, policymakers in states and cities – including Maine Gov. Janet Mills – have committed to work to achieve the greenhouse gas emissions reductions and renewable energy goals contained in the agreement.

While debate over climate policy continues in Washington, states such as Maine are already seeing clear impacts from a changing climate, particularly in the waters of the Gulf of Maine.

Maine fishermen routinely see species once found only in Southern or mid-Atlantic states while stocks of northern shrimp and cod have been depleted or moved north to cooler waters. There is also growing concern about the long-term future of Maine’s lobster industry – by far the state’s largest fishery – as waters become more acidic and the Gulf of Maine warms faster than most other areas of the ocean around the globe.

A massive federal report released in late-2018, for instance, warned that New England states are seeing some of the nation’s fastest climate shifts. Annual average temperatures in New England rose by roughly 3 degrees since the beginning of the last century compared to 1.8 degrees in the contiguous United States, the  report said.

While warming temperatures will lead to a longer agricultural growing season in Maine, those changes could also shorten the season for skiers and snowmobilers, reduce production of maple syrup and bring even more infectious diseases from ticks, mosquitoes and other pests.


But studies, including the Union of Concerned Scientists report, also acknowledge that conditions could change depending on the success of efforts to reduce greenhouse gas emissions as well as natural factors.

Bob and Christina Asbell stretch following their workout at Back Cove in Portland on Monday. Christina said that if the temperatures were hotter, such as in the nineties, they would probably ride their bikes instead of running. Derek Davis/Staff Photographer

A 2018 study by researchers at the University of Maine’s Climate Change Institute noted that factors such as volcanic eruptions, more El Nino weather patterns and the collapse of Arctic sea ice all will affect what happens in agriculture and fisheries along Maine’s coastal areas.

“In closing, the key message is that Maine should expect significant environmental changes as human and other factors create increased instability in the climate system,” reads the report, entitled Coastal Maine Climate Futures. “We suggest that the best approach to planning, adapting to and operating successfully within uncertainty is to be prepared for a variety of changes ranging from a general warming trend to occasional annual scale diversions to cooler and drier weather associated with volcanic and El Niño events, respectively.”

Spanger-Siegfried, with the Union of Concerned Scientists, whose family lives in Maine, said she and other researchers were surprised by the increase in “extreme heat” events even under a scenario where global temperatures rise by 2 degrees Celsius (3.6 degrees Fahrenheit). She said governments and citizens need to be working aggressively to meet that goal or better.

“We need to challenge ourselves first to recognize the path that we are on and to recognize the absolute urgency of moving away from it,” she said.

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