Researchers have found that the amount of green spaces and shade in a neighborhood can significantly shape temperatures. On average, neighborhoods with more trees and green spaces - instead of impervious surfaces like asphalt - can be 1 to 7 degrees Fahrenheit cooler. The phenomenon, which has been well-studied in larger urban cities, is called the 'heat island effect'. But researchers have done much less work examining how these trends play out in more rural parts of the country.
Missoula, Montana, is helping to fill that gap. In 2024, Climate Smart Missoula, a local non-governmental organization, teamed up with the city and county of Missoula and secured federal funding for a heat mapping initiative. Last summer, teams of volunteers drove transects across the county with sensors recording temperature and humidity measurements by the second. Then, analysts from the climate adaptation consulting firm CAPA Strategies turned the data into a heat map now available to the public. It's the first of its kind in the state and the Rocky Mountain region.
The research is especially important because Missoula has historically had hot and dry summers. Temperatures in western Montana's county would rise into the 80s, with occasional streaks into the 90s, before cooling off rapidly after sunset. But that pattern has changed in recent years, with hotter summers and warmer nights. The area is already experiencing more days with temperatures above 90 degrees F per 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 public infrastructure were built for cooler climates. Montana has one of the lowest rates of residential air conditioning in the country. When the heat rises, Montanans don't have the same infrastructure that Arizonans or Texans do to stay cool.
Researchers found that temperatures can vary by about 20 degrees across Missoula County depending on the prevalence of tree shade and other green spaces. Susan Teitelman of Climate Smart Missoula said their findings reflect heat maps in other larger cities across the country.
'What we're seeing in Missoula is a reflection of larger cities like New York and Boston', she said. 'You see the same thing happening everywhere: poorer and hotter neighborhoods have fewer trees; richer and 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 the Westside.
'Places where we expected to have heat islands were downtown Missoula, around the Southgate Mall, more urban and developed areas', said Kane.
But there were surprises, including how dry and brown areas, like a vacant lot in the city, acted as heat islands, according to Kane. These unmanaged and undeveloped spaces tend to be a draw for invasive species that adapt quickly to hot and dry conditions. When they're not watered and not replaced with native species, they can act as heat islands, said Kane. The research showed that heavily forested areas like Seeley Lake and Evaro, a rural area north of the city center with dense trees, also retained heat at night.
'You'll see, especially on the morning map, they're retaining heat from the previous day due to that dense canopy, and that effect is resulting in some of the highest morning temperatures recorded', said Kane.
Agencies like the National Weather Service have consistently identified heat as the deadliest type of weather Americans experience. Research from the University of Montana published in 2024 found that for every 1 degree Celsius increase in temperature, emergency calls increased by 1 percent. Many of those calls came from rural areas with older and retired populations that are more susceptible to extreme heat.
The city and county of Missoula and Climate Smart launched a campaign called Stay Cool Missoula to build community resilience to extreme heat and try to prevent those deaths. Teitelman of Climate Smart Missoula emphasized that it's crucial to prepare communities for what's coming.
'Extreme heat is dangerous', she said. 'It's affecting Missoula and Montana. It's affecting northern climates and it's an equity issue.'
Teitelman leads Climate Smart's efforts to plant trees in low-income neighborhoods where tree cover is sparse or non-existent. Having access to the heat map helped her target those planting efforts. The map has been used in other ways too, like conversations about the proposed data center in Bonner along the Blackfoot River. That project was ultimately canceled by the property manager. But Kane said being able to show just how much hotter that area is, due to the amount of land cleared for industrial use, will help inform the county in future regulations and decisions.
Missoula was one of 11 communities, including New Orleans, Memphis, Buffalo, and Moab, among others, that NOAA funded as part of a national effort to map heat islands in 2025. But the work almost didn't happen.
Like many federal projects related to global warming, it was targeted by the Trump administration. Kane, Teitelman, and their other partners had been awarded the NOAA funding in 2024. The money was allocated in the 2022 Inflation Reduction Act, the climate law passed by Congress. The Trump administration then canceled the funding in May 2025.
Half of the money had been spent or allocated to partners before the funding was canceled, but Teitelman said it was a team effort to carry out the work after the funds were rescinded. Climate Smart, along with the city and county of Missoula, had the personnel to continue the work, but they also relied on free assistance from CAPA Strategies and other national collaborators.
'They did all that work pro bono for our community and other communities. That was a blessing for us and communities across the US who were able to do this heat mapping in the face of federal funding being revoked', said Teitelman.
Kane said the lack of funding doesn't change the reality of a warming world.
'There's been so much challenge and change due to what's happening at the federal level', she said. 'But I think our local governments and our local organizations are very well-positioned to keep working on this, and that's why we're putting everything we can behind it.'
Source / Reference: Climate Central