Trends in extremes of surface humidity, temperature, and summertime heat stress in China

In the past half century, the mean summertime temperature in China has increased, with nights warming more than days. Using surface station observations, we show that the frequency of extreme heat-stress events in China, caused by extremely hot and humid days as well as by heatwaves lasting for a few days, has increased over the period from 1951 to 1994. When humidity is high, hot weather can cause heat stress in humans. The increased heat-stress trend may pose a public health problem.