Fort Collins just logged its warmest summer on record. Nighttime lows aren’t dropping the way they used to. And through most of September, nearly every day has landed above the historical average for the month.
For Colorado State University students, that’s more than a matter of sweating through class; researchers say it could be shaping how well they sleep, focus and cope with the everyday stress of college.
“Obviously we know that heat is both a physical and a psychological stressor,” said Patricia Aloise-Young, a CSU psychology professor.
Allie Mazurek, an engagement climatologist with the Colorado Climate Center at CSU, said this year’s heat has been unusual even by the standards of a warming state. Mazurek earned her doctorate from CSU’s department of atmospheric science before joining the Colorado Climate Center in January 2025.
Fort Collins recorded its warmest August on record this year, and Colorado saw its second-warmest August statewide, Mazurek said. She added that through most of September, nearly every daily weather observation at the CSU campus station has landed above the historical average for the month.
The driver isn’t necessarily hotter afternoons, she said. Overnight lows aren’t cooling off the way they once did, which is important for sleep and anyone living without air conditioning.
Mazurek also pointed to March, when Fort Collins broke its monthly temperature record by 10 degrees Fahrenheit and hit 90 degrees for the first time before May, something the city had never recorded that early in the year. She said a single month can be a statistical outlier, but the broader trend toward warming, especially in September, is not.
“All of our months are getting warmer, but September is one that we’ve seen that’s getting warmer at a quicker rate than some of the other months of the year,” Mazurek said.
She also noted that Fort Collins’ urban core — with its concrete and buildings — tends to run a few degrees warmer than the surrounding countryside, a well-documented effect known as an urban heat island.
Aloise-Young said in addition to making life more uncomfortable, heat wears down the mental resources students need to get through midterms, roommate conflicts and everything else fall semester throws at them.
“Each additional stressor that a student experiences depletes those resources,” Aloise-Young said. “And so they’re not able to study and to perform well in the classroom, and then that creates an additional stressor on top.”
She pointed to research on people in extreme heat, including outdoor workers, showing reduced productivity, more errors and worse memory performance. Heat has also been linked to increased irritability, she said, citing studies of incarcerated populations that found more disciplinary problems during hot spells in facilities without air conditioning.
A 2018 study from Harvard University’s T.H. Chan School of Public Health offers a clue as to why. Researchers tracked college students through a heat wave and found those sleeping in dorms without air conditioning did measurably worse on cognitive tests than classmates in cooled buildings.
Aloise-Young said she’s especially concerned about three groups of CSU students: first-year students already under stress due to their new environment, students without air conditioning in their housing and students on SSRIs, a class of antidepressants that, according to Aloise-Young, can interfere with the body’s ability to regulate temperature and sweat.
Roughly half of CSU’s on-campus dorms have air conditioning. Some halls, such as Academic Village, Summit Hall and part of Braiden Hall, offer air conditioning as an amenity, but a number of other halls do not.
Aloise-Young said the gap reflects the time period when buildings in Colorado were constructed. Many CSU dorms and campus buildings went up in the ’60s and ’70s, before air conditioning was standard practice in Colorado, unlike in hotter, more humid states such as Florida or Arizona.
“With climate change, the need for air conditioning is increasing, but the building stock was built before that need was really urgent,” Aloise-Young said.
Retrofitting older buildings is expensive, she acknowledged, which raises questions around prioritization of spending that CSU will likely have to confront as summers and early falls continue to warm.
In the meantime, Aloise-Young suggested short-term fixes: cooling centers on days above 100 degrees, wider distribution of water and fans and basic heat education, like wetting a washcloth to place on the back of the neck.
Mazurek said the rest of September is expected to stay above average, and while longer-range outlooks show more uncertainty heading into October, wetter conditions could bring cloud cover that helps temper the heat later this fall.
For now, both researchers agree the trend line points in the same direction: warmer.
Reach Maci Lesh at science@collegian.com or on social media @macileshmedia.
