Two foreign tourists stand by a mist sprayer to get some relief from the scorching heat at the Bund in Shanghai yesterday. The temperature touched 37 degrees Celsius yesterday.

It was the hottest day of the year in Shanghai yesterday, and even though the temperatures may drop marginally over the next few days there will be little respite from the heat wave in the city.

At 37 degrees Celsius yesterday, it was the third high-temperature day — when the mercury crosses 35 degrees — of the year. The previous two high-temperature days were recorded in May.

At 9:43am yesterday, the Shanghai Meteorological Bureau issued the year’s first orange alert for heat, warning that the mercury would touch 37 degrees in the coming hours. Pressed by the subtropical high, the temperature climbed quickly.

An hour later, the downtown Xujiahui weather station recorded the mercury at 35 degrees, eventually rising to 36.7 degrees by 3pm.

The Pudong New Area, meanwhile, was sweltering at 37.2 degrees, becoming the city’s hottest district. Qingpu District was second at 37.1 degrees, followed by Baoshan District with a reading of 37 degrees.

A beautiful solar halo over the sky caught some citizens by surprise yesterday. The luminous halo surrounding the sun was caused by clouds of ice crystals. Usually, it suggests either more scorching days ahead or a coming thunderstorm.

The high today will stay at 37 degrees. Scattered showers and thunderstorms are likely in the afternoon and in the evening.

The subtropical high is predicted to move southward tomorrow that will bring the temperature down slightly to 34 degrees. Weather forecasters said heavy rain will lash the lower reaches of the Yangtze River, which is in the midst of the plum rain season.

The high will further drop to 31 degrees on Friday and 30 degrees over the weekend. But the extreme high humidity means the general uneasiness and discomfort will remain.

Shanghai entered the annual plum rain season on June 19. The season is forecast to be shorter than usual, meaning less rain for the region. Over the period, it is not rare to have high-temperature days.

Records from 2007 to 2017 showed there were 36 high-temperature days during the plum rain season. The hottest day was in 2007 when the mercury hit 38.6 degrees.

At the end of the plum rain season, the city will enter the hottest days, or sanfu in the Chinese lunar calendar.