Rainfall in Downtown Los Angeles Throughout the Months The Los Angeles River is not like rivers we would expect to see in areas with mild climates. It is more like rivers in dry climates that change with the seasons. Those types of rivers have little or no flow through much of the year, and heavy flows and flooding through the rainy season. Likewise, the Los Angeles River is the same. Through the dry season from June to October the river has little or no natural flow. The rainy season is from November to May, and in these months floods along the river have caused more property damage and deaths than earthquakes.