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.  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 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.

 

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).

 

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.

​

​

Editor's note: This article was adapted from " Hourly Weather Data Reveals Climate Trends in U.S. " which originally appeared at https://news.ncsu.edu/2025/11/hourly-weather-data-reveals-climate-trends-in-u-s/