Sweltering Summer Nights

Since 1970, average summer nighttime temperatures have increased in 95% of 241 analyzed U.S. locations, warming by an average of 3°F. These 'sweltering nights' are warming faster than daytime highs and increase heat stress, particularly for vulnerable populations and low-income households lacking air conditioning. The document highlights that the western U.S. has experienced the greatest warming, with Reno, Nevada, seeing the highest increase at 17.4°F.

• Summer nighttime temperatures in the U.S. are rising faster than daytime temperatures. Since 1895, summer minimum temperatures have warmed at a rate of 1.64°F per century, which is nearly double the warming rate of average summer daytime highs over the same period.
• Analysis of 241 U.S. locations from 1970 to 2022 shows that summer nights warmed by 2.7°F across the contiguous U.S. Specifically, 230 locations (95% of the sample) saw warming, with an average increase of 3°F. One-quarter of these locations experienced warming of 4°F or more.
• The western U.S. experienced the most significant summer nighttime warming. Regional averages include the Southwest (3.8°F), West (3.5°F), and Northwest (3.5°F). The highest individual location increases were recorded in Reno, Nev. (17.4°F), Las Vegas, Nev. (9.6°F), El Paso, Texas (8.2°F), Salt Lake City, Utah (7.7°F), Boise, Idaho (7.1°F), and Medford, Ore. (7.1°F).
• Warming nights exacerbate health risks and energy demands. Sweltering nights limit the body's ability to cool down, increasing stress for the elderly, children, outdoor workers, and those with chronic illnesses. This is compounded in urban heat islands and low-income neighborhoods where air conditioning is less accessible, leading to higher energy bills and increased carbon pollution from higher AC usage.
• Climate change, specifically carbon pollution, is driving the increased frequency of co-occurring extreme heat days and nights. A 2020 study indicates these events became more frequent and intense across the Northern Hemisphere from 1960 to 2012, and could occur four to eight times more often by 2100 if high levels of carbon pollution continue.

APA

Morello-Frosch, R. (2023). Sweltering Summer Nights. Climate Central. https://www.climatecentral.org/climate-matters/sweltering-summer-nights-2023

Chicago

Morello-Frosch, Rachel. Sweltering Summer Nights. Climate Central, 2023. https://www.climatecentral.org/climate-matters/sweltering-summer-nights-2023.

Wikipedia

{{cite report |last1=Morello-Frosch |first1=Rachel |title=Sweltering Summer Nights |publisher=Climate Central |date=28 June 2023 |url=https://www.climatecentral.org/climate-matters/sweltering-summer-nights-2023 |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{morellofrosch2023sweltering, author = {Morello-Frosch, Rachel}, title = {{Sweltering Summer Nights}}, institution = {Climate Central}, year = {2023}, month = jun, url = {https://www.climatecentral.org/climate-matters/sweltering-summer-nights-2023}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }