A woman rides a bicycle in Shanghai on May 15, 2018.

Dong Jun / SHINE

A man protects himself from the sun as he rides a scooter in Shanghai on May 15, 2018.

Dong Jun / SHINE

A woman rides a bicycle with a boy in Shanghai on May 15, 2018.

Dong Jun / SHINE

People drink as a way to get relief from the heat as they walk on a street in Shanghai on May 15, 2018.

Dong Jun / SHINE

A woman waits to cross a street in Shanghai on May 15, 2018.

There's no doubt that Shanghai entered summer last Saturday, even if it's not official, and the scorching highs are set to hang around until Thursday, forecasters said.

Meteorologically, five consecutive days with average temperatures above 22 degrees are required in order to officially declare that summer has arrived.

For three consecutive days since last Saturday, daily average temperature have reached over 22 degrees. On Monday, the Xujiahui weather station recorded a high of 31.3 degrees, marking the hottest day this year and the second 30-plus high detected this month.

There has been no relief from the scorching weather on Tuesday. The mercury quickly climbed to 25 degrees by 7:15am. As temperatures continued soaring, the Shanghai Meteorological Bureau at 12:03pm issued a yellow high temperature alert, the lowest of a three-tier warning system, forecasting a high of 35 degrees in Jiading, Baoshan, Qingpu and Chongming districts.

The high is set to remain stable and hover around 34 and 35 degrees on Wednesday and Thursday, but it may rocket to 37 degrees in Baoshan and Jiading districts. Scattered thunderstorms may occur during the afternoons, the weather authority said.

Under the influence of a cold front, the high will decrease a little bit on Friday to 31 degrees. On Saturday, it will sharply plummet to 25 degrees, and the low will return to 20 degrees.

Historical records show Shanghai has only seen seven “high temperature days” in May, where highs hit 35 degrees, since 1873.

Shanghai usually officially enters summer around May 28.