Historical hourly weather data has given researchers a clearer picture of climate trends in the U.S. In a recent study, a team from North Carolina State University (NC State) found that over the past 45 years, some parts of the U.S. have lost the equivalent of nearly 1.5 weeks of temperatures below freezing. Conversely, other areas have gained a similar number of days of temperatures that cause heat stress.
“While information based on daily metrics is useful and informative, it does not capture the full story,” states the study. “Daily statistics do not convey the instantaneous and time-integrated impacts of weather such as precipitating storms, cloudiness changes and air mass movements (e.g., fronts).”
Researchers analyzed hourly weather station data from the National Centers for Environmental Information’s (NCEI’s) Integrated Surface Database Lite (ISD-Lite) for 340 stations in the contiguous U.S. and southern Canada from 1978 to 2023. Overall, they found that the most dramatic impacts were in the northeastern U.S. during winter, where some areas have lost the equivalent of about 1.5 to 2 weeks of temperatures below 32°F (0°C).
They also found that some parts of the U.S. – locations in Arizona, New Mexico, and parts of southern Nevada, southern California and southern Texas – have gained the equivalent of 1.5 weeks of temperatures higher than 86°F (30°C), a threshold at which crops and animals start to experience heat stress symptoms.
Some areas, such as the Midwest, showed no significant trends due to high year-to-year temperature variability.
The researchers hope the data will help policymakers, businesses and homeowners justify and plan climate adaptations.
“The U.S. is a big country, so changes will look different depending on your region,” says Sandra Yuter, Distinguished Professor of Marine, Earth and Atmospheric Sciences at NC State and one of the authors of the study. “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.”