The Union's lead climate analyst, Erika Spanger-Siegfried, says the research used historic data from 1971 to 2000 to make future projections.
"With no action by late century, each of Maine's three largest cities would experience more than two weeks worth of days with a heat index above 100 degrees," Spanger-Siegfried says.
From 1971 to 2000, Portland never had a day with a heat index above 100. But under current climate change projections, she says, that number would grow to 17 days.
"When we look around the country, that's what Montgomery, Alabama experiences today," Spanger-Siegfried says. " That's what Savannah and Las Vegas experience."
Spanger-Siegfried says the U.S. is at a critical juncture, but says it's not too late to take meaningful action to combat climate change, such as reducing emissions.
Originally published July 16, 2019 at 6:00 a.m. ET.