On the morning of August 31, the Shanghai Central Meteorological Observatory issued another yellow high-temperature warning. This means the city has once again broken two meteorological records: the longest consecutive high-temperature days and the most high-temperature days in August.

Around 11:00 a.m. on August 31, the temperature at the Xujiahui weather station in Shanghai surged past the 35-degree Celsius high-temperature mark, marking the 45th high-temperature day of the year and the 26th consecutive day of high temperatures since August 6. This not only broke the record for consecutive high-temperature days since 1926 but also set a new record for the most high-temperature days in August.

According to the Shanghai Meteorological Department, the first high-temperature day this year occurred on June 17, about 10 days earlier than usual. Since then, Shanghai’s high temperatures have been characterized by an early start, high frequency, and long duration, entering an “ultra-long standby” mode.

Since meteorological records began in Shanghai in 1873, the longest consecutive high-temperature period was 24 days from July 22 to August 14, 1926. That record was broken this year: on August 30, Shanghai reached 25 consecutive high-temperature days, and on August 31, it set a new record with 26 consecutive high-temperature days.

This August, Shanghai experienced 27 high-temperature days, surpassing last August’s 26 high-temperature days and setting a new record for the most high-temperature days in August since 1951.

The Shanghai Meteorological Department stated that the core reason for this year’s persistent high temperatures in Shanghai is the abnormal activity of the Northwestern Pacific Subtropical High (referred to as the “subtropical high”). In early to mid-June, the subtropical high was positioned farther west and north and was stronger than usual, creating conditions for an early onset of high temperatures. In early and late July, influenced by typhoons, the subtropical high temporarily retreated south and east, providing brief relief from the heat. After August, the main body of the subtropical high strengthened again and stably controlled the Yangtze River Delta, triggering this round of persistent high temperatures.

Meteorological forecasts indicate that due to the influence of westerly troughs and cold air infiltration, the subtropical high will temporarily retreat south and east starting August 31, moving away from southern China. Most areas in the south will experience a pause in high temperatures for 3 to 5 days. Shanghai will also briefly escape the persistent heat. However, as the subtropical high extends westward and northward again by September 3, the city is expected to face the return of the “autumn tiger.”

Shanghai Central Meteorological Observatory

The Shanghai Central Meteorological Observatory, established in 1872 by the French Catholic Mission, is one of the oldest meteorological stations in East Asia. It has played a vital role in recording the city’s climate data for over a century. Today, it continues to function as a key institution for weather forecasting and meteorological research in the Shanghai region.

Xujiahui weather station

The Xujiahui Observatory is a historic weather station established in 1872 by the French Jesuit mission in Shanghai. It was one of the first modern observatories in East Asia and played a pivotal role in the development of meteorology in China. While its original function has been superseded, its historic building remains a cultural landmark.

Northwestern Pacific Subtropical High

The Northwestern Pacific Subtropical High is a semi-permanent high-pressure system in the atmosphere over the northwestern Pacific Ocean. It is a major component of the East Asian monsoon system, significantly influencing the region’s climate by directing moist air and seasonal rainfall. Its strength and position have historically dictated weather patterns, including the timing of the Mei-yu front’s heavy rains in China.

Yangtze River Delta

The Yangtze River Delta is a fertile and economically vital region in eastern China, historically known as the “Land of Fish and Rice” and a cradle of Wu and Yue culture. It has been a major center of trade, commerce, and innovation since the era of the Grand Canal and is now one of the world’s most important economic hubs.