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 incr eased, with nights warming more than days. Using surface station observatio ns, we show that the frequency of extreme heat-stress events in China, caus ed by extremely hot and humid days as well as by heatwaves lasting for a fe w days, has increased over the period from 1951 to 1994. When humidity is h igh, hot weather can cause heat stress in humans. The increased heat-stress trend may pose a public health problem.