Boulder built its own climate models. Here’s what they say about the next 25 years.

As Boulder braces for a hotter, drier future, new climate models tailored specifically to the city are providing a clearer picture of the risks ahead. By 2030, Boulder could see almost 30 days above 95 degrees, 200 high fire-risk days and several extreme precipitation events annually — a dramatic shift from historical norms.

The city commissioned these projections as part of its expanding climate resilience efforts, aiming to equip residents, businesses and policymakers with data to guide adaptation and mitigation strategies.

The models were developed by Resilience Analytics using observational data from the University of Colorado. They refine global climate projections to a hyperlocal scale, accounting for Boulder’s unique topography and climate patterns.

“Grid cells in global climate models can be up to 100 miles wide, so they aren’t really sufficient for analyzing local impacts,” said Kate Galbo, a sustainability data analyst for the city. Boulder is among the first communities of its size to develop downscaled climate models tailored specifically to its geography.

The city focused on heat, extreme precipitation, drought and fire risk — the most pressing climate threats for Boulder.

Boulder has already seen dramatic changes. Historic data, averaged from 1986 to 2005, provided the city a baseline for comparison, said Brett KenCairn, the city’s senior policy adviser for climate and resilience. He said his wife, who was born in Boulder, has witnessed the shift firsthand.

“In the course of a generation, she’s gone from seeing temperate afternoon thunderstorms — and you never needed air conditioning — to the very different circumstances we live in now.”

The climate shift: Then, now and what’s next

To understand how much Boulder’s climate has changed, researchers compared past and present conditions:

Historic Baseline (1986–2005):

• 5 days per year over 95°F
• 14 high fire-risk days per year
• 1 extreme precipitation event every 5 years

Recent Data (2018–2022):

• 10 days per year over 95°F
• 116 high fire-risk days per year
• 57 drought days per year
• 3-day heatwave maximum average: 98°F

Projected by 2030:

• 28 or more days per year over 95°F
• 192 high fire-risk days per year
• 2.5 extreme precipitation events every 5 years
• 151 or more drought days per year
• 3-day heatwave maximum average: 101°F

Projected by 2050:

• 42 or more days per year over 95°F
• 230 or more high fire-risk days — about two-thirds of the year
• 2.5 extreme precipitation events every 5 years
• 170 drought days per year
• Heatwaves reaching 103°F

These findings confirm what many Boulder residents are already experiencing: longer, hotter summers and more frequent extreme weather events.

“If a person is thinking, ‘We’ve just had a few hot years, but it will go back to something else,’ that’s probably not going to be the case,” KenCairn said.

What can be done?

Boulder is looking for ways to blunt the worst of the heat and fire risks. Galbo said the city worked with a team from Georgia Tech to model different cooling methods.

“We see a pretty significant amount of cooling by increasing tree canopy, as well as a pretty stark increase in temperature from losing tree canopy,” Galbo said.

Boulder’s Community Forest Corps is already working to maintain the city’s trees and gather local heat data. But KenCairn warns that simply planting more drought-resistant trees from warmer climates won’t be enough, since Boulder still experiences extreme cold snaps that these trees wouldn’t tolerate.

Beyond tree cover, other possible climate adaptations include burying power lines to reduce wildfire risk, expanding HVAC systems in schools and other buildings that historically didn’t need them, and investing in distributed energy storage for a more reliable power grid.

The city also hopes to map out the most vulnerable populations, including low-income residents, seniors and people living near canyon mouths — areas prone to extreme climate impacts.

“That’s going to be a really important part of helping us,” KenCairn said, “because we can’t act everywhere at full scale.”

KenCairn sees the climate models as a tool to engage the community and highlight risks, especially in higher-risk areas.

“We need to ground that truth with our community itself,” he said. The latest data will be publicly accessible through a Climate Action Plan the city plans to release this spring.

He hopes this leads to stronger tree protection ordinances and landscaping codes designed to enhance hydration and cooling.

Boulder City Councilmembers are working to amend the city’s zoning and building codes to limit flammable landscaping and building materials. This could include prohibiting highly flammable plants and trees, such as junipers, in new landscaping projects. They also want the city to require water-efficient landscaping with drought-tolerant plants while strengthening tree protection ordinances and landscaping codes.

KenCairn also encourages residents to assess their own homes and landscapes for ways to improve resilience. This could include learning about heat pumps or installing pollinator habitats that use less water and provide cooling.

He said climate experts no longer understand nature as just something visually appealing or a place for recreation. “It’s literally providing critical life support services.”

While the new models provide a roadmap, climate projections are not guarantees. Climate change can progress in nonlinear ways, KenCairn explained.

“You reach certain thresholds, or tipping points, after which a whole series of other things happen,” he said. “You get things warm enough, and suddenly a whole ice sheet slides off, and then that changes the whole dynamic.”

Losing an entire ice sheet, for example, could disrupt a critical Atlantic Ocean current that helps maintain Northern Europe’s temperate climate, potentially triggering widespread changes.

To ensure accuracy, scientists test models against historical data. While the future will never perfectly match projections, strong models increase confidence in general trends.

KenCairn expects the city to update its climate models in the next two to three years as technology advances and more data becomes available.

Correction: An earlier version of this story misstated the frequency of extreme precipitation events due to a data issue. Updated figures clarify that the projections refer to totals over 20-year periods, not annually. By 2050, Boulder is expected to see 12 such events every 20 years — or about 3 every five years.