As Montana warms, Missoula’s first heat map reveals hidden hotspots
Grist · LC · trust 49/100
Researchers have found that the amount of green space and shade in a neighborhood can significantly shape temperatures. On average, neighborhoods with more trees and green space — instead of impermeable surfaces like pavement — can run anywhere from 1 to 7 degrees Fahrenheit cooler. The phenomenon, which has been well studied in major urban cities, is called the “heat island effect.” But researchers have done far less work examining how those trends play out in more rural parts of the country.
Missoula, Montana, is helping fill that gap. In 2024, Climate Smart Missoula, a local nonprofit, teamed up with the city and county of Missoula and secured federal funding for a heat mapping initiative. Last summer, teams of volunteers drove countywide transects with sensors recording second-by-second measurements of temperature and humidity. Then analysts with the climate adaptation consulting firm CAPA Strategies turned the data into a now-publicly available heat map for the county . It’s the first of its kind for the state and this region of the Rockies. (Cities in Wyoming, North Dakota, and South Dakota also do not have heat maps.)
The research is especially important because Missoula has historically had warm, dry summers. Temperatures in the western Montana county climb into the 80s, with occasional stretches in the 90s, before cooling off sharply after sunset. But that pattern has shifted in recent years, with hotter summers and warmer nights. The area is already experiencing more days with temperatures above 90 degrees F each year. The county’s average annual temperature is projected to increase by 4 to 5 degrees F by 2050 .
The change poses particular challenges for places like Missoula, where homes, buildings, and other public infrastructure were built for cooler climates. Montana has one of the lowest rates of residential air conditioning in the country. When the heat builds, Montanans don’t have the same infrastructure as Arizonans or Texans to keep cool.
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The researchers found that temperatures can vary by nearly 20 degrees across Missoula County depending on the prevalence of shade from trees and other green spaces. Susan Teitelman, with Climate Smart Missoula, said their findings mirror heat maps in other larger cities across the country.
“What we’re seeing in Missoula mimics larger cities like New York and Boston,” she said. “You see the same thing happening everywhere: Poorer, hotter neighborhoods have fewer trees; wealthier, greener neighborhoods have lower temperatures.”
Alli Kane, the county’s climate action program coordinator, said some of the results weren’t surprising. Neighborhoods like the University District or the Rattlesnake, where large, mature trees provide shade, were significantly cooler than the Northside or Westside.
“Places where we anticipated we would have heat islands were downtown Missoula, around Southgate Mall, those areas that are more urban and more built up,” Kane said.
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But there were surprises, too, including how dry, brown open lands, like an empty lot in town, acted as heat islands, according to Kane. These unmanaged and undeveloped spaces tend to be a magnet for invasive species that quickly adapt to hot and dry conditions. When they’re left unwatered and not replaced with native species, they can act as heat islands, Kane said. The research showed heavily forested places like Seeley Lake and Evaro, a rural area north of the city center with dense trees, also held on to heat overnight.
“You’ll see, especially in the morning map, they are retaining heat from the day before because of that really dense canopy, and so that effect is resulting in some of our highest-recorded morning temperatures,” Kane said.
Agencies like the National Weather Service have consistently identified heat as the most deadly weather Americans experience. Research from the University of Montana published in 2024 found that for every 1 degree Celsius temperature increase, 911 calls increased correspondingly by 1 percent. Many of those calls came from rural areas with older, retired populations that are more susceptible to extreme heat.
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