Group 1 - The article discusses the strongest heatwave of the year affecting various regions in China, with temperatures exceeding 40°C in some areas [1][3] - The Central Meteorological Observatory has issued a yellow warning for high temperatures, indicating widespread high temperatures across more than 2 million square kilometers [1][3] - The heatwave is attributed to the influence of the subtropical high-pressure system, which is expected to continue affecting northern regions for the upcoming week [3][4] Group 2 - Experts clarify that the current humid and hot weather in northern China is not accurately described as "returning to southern weather," but rather as "sauna weather" due to its specific characteristics [2][3] - The high humidity and temperature combination can lead to health risks, including heatstroke and cardiovascular issues, necessitating public awareness and preventive measures [4][6] - The phenomenon of "cold heatstroke" is highlighted, where individuals may experience heat-related symptoms due to sudden temperature changes between air-conditioned environments and outdoor heat [5][6][7]