Warm Summer Nights

Since 1970, average summer nights in the contiguous U.S. have warmed by 2.5°F, with nighttime temperatures warming nearly twice as fast as daytime temperatures since 1895. Using the Climate Shift Index (CSI), Climate Central finds that climate change makes warm summer nights significantly more likely than warm days, posing health risks and increasing cooling costs.

• Summer nighttime (minimum) temperatures are warming significantly faster than daytime (maximum) temperatures. Since 1895, summer minimums across the U.S. have risen at a rate of +1.58°F per century, which is nearly double the warming rate of summer maximums over the same period.
• Between 1970 and 2021, average summer nighttime temperatures in the contiguous U.S. increased by 2.5°F. In 40% of 246 analyzed U.S. locations, this warming was at least 3°F, and nearly 25% of those locations saw increases of at least 4°F. The highest overnight warming since 1970 occurred in Reno, Nev. (+17.3°F), Las Vegas, Nev. (+9.5°F), El Paso, Texas (+8.1°F), Salt Lake City, Utah (+7.3°F), and Boise, Idaho (+6.9°F).
• The Climate Shift Index (CSI) indicates that human-caused climate change has a stronger influence on nighttime lows than daytime highs. For the period of July 1-15, 2022, 86% of the U.S. population (78% of the continental U.S.) experienced nighttime lows made at least twice as likely by climate change, compared to 20% of the population (24% of the continental U.S.) for daytime highs.
• Elevated nighttime temperatures create health risks because they prevent recovery from hot days, particularly for vulnerable groups such as the elderly, young children, outdoor workers, and those in urban heat islands or lower-income neighborhoods. Additionally, 95% of 246 U.S. locations have seen a rise in cooling degree days since 1970, increasing energy costs and potentially increasing emissions if air conditioning is powered by fossil fuels.

APA

Climate Central (2022). Warm Summer Nights. https://www.climatecentral.org/climate-matters/warm-summer-nights-2022

Chicago

Climate Central. Warm Summer Nights. 2022. https://www.climatecentral.org/climate-matters/warm-summer-nights-2022.

Wikipedia

{{cite report |author=Climate Central |title=Warm Summer Nights |date=20 July 2022 |url=https://www.climatecentral.org/climate-matters/warm-summer-nights-2022 |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{climatecentral2022warm, author = {{Climate Central}}, title = {{Warm Summer Nights}}, institution = {Climate Central}, year = {2022}, month = jul, url = {https://www.climatecentral.org/climate-matters/warm-summer-nights-2022}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }