Flood season: the flood season is the appearance of water, and the flood season is the period when rivers are full of water.
Rainy season: refers to the period when river flow depends on rainfall or snowmelt.
2. Different duration:
The rainy season lasts longer than the flood season. The rainy season includes the flood season, but the flood season is shorter than the rainy season. For example, the rainy season of the Yangtze River is May 5- 10/0, while its flood season is rainy season (mid-June-mid-July) and winter is dry season.