Warm start to week then cold and thunderstorms

The mercury is expected to hit 30 degrees Celsius again early this week with sunny and dry days but rain and colder weather will return by Wednesday.

According to the Shanghai Meteorological Bureau, this Mother's Day on Sunday was cooler and wetter compared with the past five years. 

Despite a high of 18.2 degrees Celsius on Mother's Day in 2016, the other four years all saw the high between 23.2 and 29.5 degrees, higher than Sunday's 22.6.

And Sunday had a rainfall of 5 millimeters, higher than 2018's 2 millimeters and 2016's 0.6, while the other three years were dry.

This week will kick off with a sunny start under the domination of northwest airflow. The temperature is expect to reach 28 with a low of 18. Suburban areas will be cooler with the mercury ranging between 14 and 16 degrees in the morning.

Morning fog is expected in parts of the city.

Sunny skies will remain in the city on Tuesday with a high of 30 and a low of 18.

However, another round of rainfall will arrive late Wednesday. Although Wednesday's high is forecast to be 29 degrees, it will soon drop to 24 degrees on Thursday with showers or thundershowers at times.

The rainy weather will be similar on Friday and Saturday with the high bouncing back to 27 and 28 degrees. Skies will clear up on Sunday and the dry conditions will last into early next week.

The low will be 20 to 22 degrees from Thursday to Sunday.

On Sunday, PM2.5 particles started to pollute the city's air from 11am. By 6pm, the air quality index increased to 139, reaching the lightly polluted level. The concentration of PM2.5 reached 106 micrograms per cubic meter, four times the guideline set by the World Health Organization of 25.

The local ecology and environment bureau forecasts that the air will be clean on Monday but ozone will be the new pollutant on Wednesday to make it a lightly polluted one again.