SHANGHAI is likely to enter autumn proper this week, forecasters said yesterday.

A cold front hit about midnight Tuesday, bringing thunderstorms. Northern and western areas such as Songjiang and Jiading districts were heaviest hit.

Rain helped cool the city dramatically — from Tuesday’s high of 30.4 degrees Celsius to barely 21 degrees yesterday morning and hovering around 20 by noon, readings from the Xujiahui observatory showed.

The cold front is set to settle over the city for the rest of the week, the Shanghai Meteorological Bureau said.

Temperatures will fluctuate between 17 and 22 until Sunday and residents should carry umbrellas for expected intermittent showers.

It is considered officially autumn when the average temperature is below 22 for five consecutive days. And the beginning of the season is counted from the first of those five days, which may turn out to have been yesterday.