United States records extreme heat and cold month rankings across multiple states

In July 2026 a heat dome over the northern Rockies drove record‑breaking temperatures in Montana, Wyoming and Utah, with all‑time highs of 111‑115°F recorded at several airports. The National Weather Service reported spikes in heat‑related emergency visits, highlighting health risks for older adults.

Separate climate analyses compiled by Stacker rank the coldest May months in Missouri and Arizona since 1895 and the hottest June months in California and Colorado over the same period. The lists show historic lows such as a 58.5°F average in May 1917 in Arizona and historic highs such as a 74.9°F average in June 2021 in California, underscoring a long‑term warming trend attributed to climate change.