LatestReuters defines “heat storms” as heat waves covering at least 1% of the globe at their peak, and its analysis finds they have grown dramatically more frequent—from about five active events a year in the 1960s to roughly 102 a year this decade. The largest recorded event lasted 367 days across 2023 and 2024 and affected nearly 85% of the planet, as prolonged extreme heat caused widespread harm; researchers say these changes have occurred alongside rising greenhouse gas emissions.Oct 20, 2026