When is the rain and dew

Rain and dew is the rainy season, not the specific time.

Rain and dew come from the Tang Dynasty poet Yuan Zhen's "Hundred Rhymes of Qujiang Old People": "It is hard when you are free, and it rains frequently in good years". Farming in idle days is rainy in good years. So rain and dew refer to a large-scale rainy season.

Solar terms are special festivals that express natural rhythm changes and establish "See you in December" in the trunk calendar.