Real-time ground temperature at 14pm on May 20, 2025. Photo: Weather China, a website affiliated with China Meteorological Administration

After northern China got in its first widespread heatwave of the year with temperatures exceeding 40°C in some areas, ground temperatures in some northern regions soared above 70 degrees, according to Weather China, a website affiliated with China Meteorological Administration, on Tuesday.

By 2 pm on Tuesday, ground temperatures in the affected areas generally surpassed 50°C, with particularly scorching readings in Yongji (71.1 C) and Pingyao (70.3 C) in North China's Shanxi Province, and Tongxin (70.1 C) in Northwest China's Ningxia Hui Autonomous Region.

In Yongji, the afternoon ground temperature briefly hit 71.5°C, not only breaking the local May record but also marking the second-highest annual reading, just behind the 71.9°C recorded on June 13, 2024.

Weather China explained that ground temperature measurements differ from the air temperatures typically reported by meteorological agencies. Air temperature is measured 1.5-2 meters above the ground in a ventilated, shaded instrument shelter, representing near-surface atmospheric conditions. These readings are usually lower than ground temperatures in summer. 

Ground temperature, however, is measured on exposed soil surfaces. During intense summer heat, especially in the afternoon, ground temperatures rise rapidly, far exceeding air temperatures recorded in shelters. 

Ground temperature is directly influenced by surface conditions. For instance, cement surfaces are significantly hotter than grassy areas under the same air temperature, said Weather China.

Weather China reported on Monday that northern China was undergoing its first widespread heatwave of the year, with some areas surpassing 40 C. Regions like Central China's Henan Province and North China's Hebei Province broke local May temperature records. 

The heatwave began on Sunday, peaking on Monday and Tuesday. Zhang Bin, a meteorologist at Weather China, said this year's heatwave arrived earlier than usual, covering a broad area with high intensity, some areas could see temperatures repeatedly exceed 40 C.

Zhang said the extreme heat in Henan and Hebei resulted from clear skies with strong solar radiation, rapidly heating the ground. Additionally, these areas lie east of the Taihang Mountains, where descending air currents further amplify temperatures.

The heatwave will continue Wednesday. By Thursday, the heatwave will begin retreating southward, Weather China said.

Global Times