The days before and after the solar term major heat is the hottest days of the summer. As the saying goes 小暑大暑無君子」There is not gentleman during the major heat and minor heat. Temperature is so hot people longer car about manners and take off their clothes, thus losing their gentlemanly image.
Afternoon rain is common, yet if there is not rain for multiple days, it implies a typhoon is coming. This is the season when typhoons are common.