Researchers from North Carolina State University have analyzed historical hourly weather data to better understand regional climate change trends in the United States. Their study, published in PLOS Climate on November 12, 2025, examined how long temperatures stay above or below certain thresholds and found notable shifts over the past four and a half decades.
Sandra Yuter, Distinguished Professor of Marine, Earth and Atmospheric Sciences at NC State and corresponding author of the study, explained: “One of the challenges when talking about and planning for climate change is that the average change seems too small to be significant. Two or three degrees doesn’t make much difference if your average daily temperature is 65 degrees Fahrenheit. But it can make a huge difference if your typical temperature was 30 F and that increases to 33 F.”
The research team used data from the National Centers for Environmental Information’s Integrated Surface Database Lite, which includes information from 340 weather stations across the contiguous U.S. and southern Canada between 1978 and 2023. They calculated decadal trends in hours spent below freezing (32°F/0°C) as well as hours above heat stress thresholds (86°F/30°C) for animals and plants.
Yuter highlighted why these measurements matter: “The length of time that temperatures exceed thresholds like the one for heat stress is important. Maximum temperatures of 90 F (32 C) recorded for six hours over the course of a day will have substantially different impacts on people, animals, plants and buildings compared to the same maximum temperature recorded for only one hour of a day.”
The findings show that many areas in the northeastern U.S., particularly those east of the Mississippi River and north of latitude 37°N, have lost approximately one-and-a-half to two weeks per year where temperatures remain below freezing compared to levels observed in the early 1980s. Meanwhile, parts of Arizona, New Mexico, southern Nevada, southern California, and southern Texas now experience about one-and-a-half more weeks each year with temperatures exceeding levels known to cause heat stress in crops and livestock.
Regions such as the Midwest did not display significant trends due to high variability in yearly temperatures.
According to Yuter: “Our main aim with this analysis is to explain how climate change is occurring in a manner that aligns with lived experiences so that people can understand it and take pragmatic action to adapt. The U.S. is a big country, so changes will look different depending on your region, but the work demonstrates that hourly temperature data is potentially useful in determining where there will be effects on ecological patterns and organism behaviors, energy usage, and growing season duration across the country.”
This research was supported by several organizations including NC State University’s Provost Professional Experience Program; NASA; Office of Naval Research; Robinson Brown Ground Climate Study donation fund; with former NC State undergraduate Logan McLaurin as first author. Other contributors from NC State include Kevin Burris (former Ph.D. student) and Matthew Miller (Senior Research Scholar).
The authors suggest their results may help policymakers, businesses, homeowners—and others—justify or plan adaptations related to changing climate conditions.
