An intransitive verb meaning to begin to fall (of rain, snow, etc.); to start precipitating.
雨が降り始めたので、傘を持って行こう。
It started to rain, so let's take an umbrella.
午後から雪が降り始める予報だ。
The forecast says snow will begin to fall from the afternoon.
小雨が降り始めたとき、私は窓を閉めた。
When the light rain began, I closed the window.
空が暗くなって、突然激しい雨が降り始めた。
The sky darkened and suddenly heavy rain began to fall.