Major Heat, or Dashu in Chinese, is the last solar term of summer, usually beginning between July 22 and 24. At this time, accumulated ground heat peaks and overlaps with the second of the three 10-day periods during the hottest part of summer (mid-July to mid-August), causing both the northern and southern regions to experience sweltering and humid "sauna weather."

During Major Heat, intense sunlight, high temperatures and frequent rainfall create oppressive heat and humidity. Despite the discomfort, these conditions are highly beneficial for crop growth, as plants thrive and develop most rapidly in this season

Traditional customs include drinking herbal tea (Fucha) to dispel the summer heat, and in coastal areas of Zhejiang, people hold ceremonies sending off the "Major Heat boat" to pray for safety and peace.