Studying historical hourly weather data – and the amount of time that temperatures remain above or below certain thresholds – reveals several impacts of U.S. regional climate change trends. In a new study, researchers from North Carolina State University found that over the past four and a half decades, areas in the northeastern U.S. have lost almost 1 1/2 weeks of temperatures below freezing, while portions of some states in the Gulf and Southwest have gained almost 1 1/2 weeks of temperatures that cause heat stress. The data can be used to inform climate adaptation planning.

“One of the challenges when talking about and planning for climate change is that the average change seems too small to be significant,” says Sandra Yuter, Distinguished Professor of Marine, Earth and Atmospheric Sciences at NC State and corresponding author of the study. “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 looked at hourly weather station data obtained from the National Centers for Environmental Information’s Integrated Surface Database Lite – which contains data from 340 weather stations in the contiguous U.S. and southern Canada – from 1978 to 2023. For each station, they computed decadal trends in hours below the freezing point (0 degrees Celsius, 32 F) and hours above the threshold for heat stress in animals and plants (30 C, 86 F).

“The length of time that temperatures exceed thresholds like the one for heat stress is important,” Yuter says. “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.”

Overall, they found that the most dramatic impacts were in the northeastern U.S. during winter. Many weather stations east of the Mississippi River and north of the 37th parallel have lost the equivalent of about 1 1/2 to 2 weeks of temperatures below 32 F (0 C).

They also found that locations in Arizona, New Mexico, and parts of southern Nevada, southern California and southern Texas have gained the equivalent of about 1 1/2 weeks of temperatures higher than 86 F (30 C), a threshold at which agricultural crops and animals start to experience heat stress symptoms.

Some areas, such as the Midwest, showed no significant trends due to the high variability of temperatures from year to year.

The researchers hope that the data can help policymakers, businesses, and homeowners justify and plan climate adaptations.

“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,” Yuter says. “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.”

The work appears in PLOS Climate and was supported by the NC State University Provost Professional Experience Program, the National Aeronautics and Space Administration (80NSSC19K0354), the Office of Naval Research (N00014-21-1-2116 and N00014-24-1-2216), and the Robinson Brown Ground Climate Study donation fund. Former NC State undergraduate student Logan McLaurin is first author. Other NC State contributors include former Ph.D. student Kevin Burris and Senior Research Scholar Matthew Miller.

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Note to editors: An abstract follows.

“The power of hourly weather data: Observed air temperature climate trends for pragmatic decision-making”

DOI: 10.1371/journal.pclm.0000736

Authors: Logan McLaurin, Sandra E. Yuter, Kevin Burris, Matthew A. Miller, North Carolina State University Published: Nov. 12, 2025 in PLOS Climate

Abstract: Analysis of hourly air temperature data from recent decades reveals trends and the degree of variability in the length of time above and below key temperature thresholds associated with the freezing point, heat stress, and energy usage. We examine hourly weather station data obtained from NOAA’s Integrated Surface Database for 340 stations in the contiguous US and southern Canada from 1978 to 2023. For each station, we compute decadal trends in hours below the freezing point (0◦ C, 32◦ F), hours above the threshold for heat stress in animals and plants (30◦ C, 86◦ F), and energy usage in terms of heating and cooling degree hours (weighted deviations from 18◦ C, 65◦ F). Many locations in southern Canada and the north central and western US lack clear decadal trends in hours below 0◦ C and have high variability in below freezing temperatures year to year. In contrast, most locations east of the Mississippi River and north of 37◦ N have lost the equivalent of ∼1.5 to 2 weeks per year of temperatures below freezing compared to the early 1980s. The same northeast region shows mostly insignificant trends in hours above 30◦ C. The largest gains in the number of hours above 30◦ C are concentrated in the southwestern US and parts of Texas. For most locations in the northern portions of the US, the rate at which heating degree hours are lost outpaces the rate at which cooling degree hours are gained. Trends in threshold exceedance are more easily related to lived experiences than incremental changes to seasonal or annual averages. Our examination of hourly data complements assessments of historical temperature changes based on daily minimum, maximum, and average temperatures. Information on regional exceedance trends and their magnitudes can aid local climate adaptation planning.