Hot Summer Days Linked to Climate Change in U.S. Cities

Analysis using the Climate Shift Index (CSI) reveals that 97% of the U.S. population experienced at least one summer day in 2023 with temperatures made at least twice as likely by climate change. The strongest impacts were concentrated in the U.S. South, Southwest, and Southeast, with San Juan, Puerto Rico, and Victoria, Texas, among the most affected cities. The period was also characterized by record-breaking heat streaks and a record number of billion-dollar weather disasters in the U.S.

• In the United States, 326 million people, representing 97% of the population, experienced at least one summer day between June 1 and August 31, 2023, where temperatures were made at least 2x more likely due to human-caused climate change.
• The U.S. South, Southwest, and Southeast were the regions most influenced by climate change; in the South, the average city had 49 summer days (53% of the season) with heat made at least 2x more likely by climate change.
• Of the 244 U.S. cities analyzed, 45 had at least half of all summer days with heat made at least 2x more likely by climate change, with the highest concentrations in Texas (17 cities) and Florida (11 cities). San Juan, Puerto Rico, was the most affected, with 90 days (98% of the summer) at this level.
• Several U.S. cities experienced record-breaking heat streaks of 100°F or higher, including Tucson, Arizona (53 consecutive days), Bryan, Texas (50 consecutive days), and Austin, Texas (45 consecutive days). Phoenix, Arizona, also set records for streaks at or above 105°F (56 days) and 110°F (31 days).
• The first eight months of 2023 saw a record 23 billion-dollar weather and climate disasters in the U.S., totaling $57.6 billion in estimated losses, surpassing the previous record of 22 set in 2020.

APA

Pershing, A. (2023). Hot Summer Days Linked to Climate Change in U.S. Cities. Climate Central. https://www.climatecentral.org/climate-matters/us-summer-2023-in-review

Chicago

Pershing, Andrew. Hot Summer Days Linked to Climate Change in U.S. Cities. Climate Central, 2023. https://www.climatecentral.org/climate-matters/us-summer-2023-in-review.

Wikipedia

{{cite report |last1=Pershing |first1=Andrew |title=Hot Summer Days Linked to Climate Change in U.S. Cities |publisher=Climate Central |date=13 September 2023 |url=https://www.climatecentral.org/climate-matters/us-summer-2023-in-review |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{pershing2023hot, author = {Pershing, Andrew}, title = {{Hot Summer Days Linked to Climate Change in U.S. Cities}}, institution = {Climate Central}, year = {2023}, month = sep, url = {https://www.climatecentral.org/climate-matters/us-summer-2023-in-review}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }