Average temperatures across the contiguous United States were the highest on record this summer, measured as a national average for June to August, with individual state records also broken.

Researchers described the result as the latest signal of anthropogenic climate change, saying the magnitude and duration are hard to explain by natural variability alone.

Social effects

The heat pushed electricity demand to repeated summer peaks. Cooling costs and heat-related illness rose with it.

Surveys have consistently found outdoor workers, older people and low-income households with limited access to cooling to be the most affected.

A comparison with East Asia

The Korean peninsula, eastern China and Japan have also seen a run of summer heat records. The mix of causes differs by region, but the long-run trend points the same way.

The next markers are winter records and sea-surface temperatures, both of which feed into forecasts for the following summer.