Group 1 - A cold air mass has affected Hangzhou, causing temperatures to drop to a maximum of 18.2℃, a decrease of 4-5℃ compared to the previous weekend [1] - The cold air's impact will end by Wednesday, with temperatures expected to rise above 20℃ in Hangzhou as the new cold air mass has not yet arrived [1] - This week will see more frequent rainfall in Hangzhou, with three expected rain events on Tuesday, Wednesday, Thursday, and the weekend, although the rainfall will be light [1] Group 2 - This autumn, an unusual phenomenon of "spring flowers blooming in autumn" has been observed in Hangzhou, where cherry blossoms and osmanthus flowers are blooming simultaneously [2] - The meteorological explanation for this phenomenon includes an unusually high average temperature of 28.8℃ in early October, followed by a significant drop in temperature due to a cold air mass [2] - The occurrence of off-season blooming serves as a warning signal regarding climate change's impact on ecosystems, as it may deplete plants' energy reserves needed for winter and future growth [2]