北京为何突降暴雨？怎么下得比预报大？疾控提示：发现自来水异常请停止饮用并上报

Group 1 - Beijing experienced heavy rainfall, with an average precipitation of 41.8 mm across the city from July 9, 16:00 to July 10, 10:00, and a maximum of 179.4 mm recorded in Yan Village, Fangshan District [1][2] - The rainfall was primarily convective, triggered by high humidity and weak cold air, leading to uneven distribution, with significant rainfall in urban and western/southern areas, while eastern regions saw minimal precipitation [2] - The Beijing CDC issued health warnings regarding drinking water safety during the flood season, advising residents to avoid contaminated water sources and to report any abnormalities in tap water [3] Group 2 - Starting from July 20, the city will enter a period of high temperatures known as "San Juan days," with expected temperatures rising to 34-35°C over the weekend [4][5] - The "San Juan days" will last for 30 days, with the shortest duration in recent years, emphasizing the need for public awareness regarding heat-related health risks [5]