The Shanghai Metrological Bureau issued this year's first yellow alert at 10:33am this morning, warning a high temperature of up to 35 degrees Celsius around noon.
Rising temperatures intensified humidity and shrouded the city in haze this morning. Showers and thunderstorms are expected in the afternoon, the bureau said.
Shanghai is still in midst of the "plum rain" season marked by weeks of rains and high humidity. Tomorrow and Wednesday will be overcast and rainy with a drop in temperature.
A yellow heat alert is the lowest of a three-color warning system after orange for temperatures above 37 degrees Celsius and red for temperatures above 40 degrees.
People cool off in water from orange-coded alert of heat in Chongqing