A woman walks through a flooded street in Shanghai's Hongkou district on Friday afternoon, when the city for the first time in four years saw a red rainstorm alert, the highest in the official four-level warning system. The Shanghai Meteorological Bureau issued an orange rainstorm alert at 1:35 pm, which was upgraded to red 26 minutes later, indicating precipitation of more than 100 millimeters. The thunderstorms also paralyzed some of Shanghai's metro lines and arterial roads, while the city's two airports - Hongqiao and Pudong - were barely affected. The highest hourly precipitation was spotted in Pudong with 124 millimeters. Photo: IC