In 1981, climate researchers began tracking hourly temperatures that would eventually span 43 years of global data. 47 years later, their projections show hot days could contain more than 4 extra hours of extreme heat, revealing risks daily averages miss

Extreme heat hours are rising faster than entire hot days globally. Hotter nights are becoming more common, extending heat exposure periods. Future projections show a significant increase in hourly heat extremes by 2100. Low-income nations face the most substantial rise in hot hours. People born today will experience more extreme heat over their lifetimes.