“外面在下雨,你应该等雨停了再走。”
It is raining outside, and you shouldn't leave until the rain has stopped.
It's raining outside. You'd better wait until it stops (raining)
It's raining outside. You should wait until the rain stops.
It is raining outside.You should stay here until the rain stops.
It's still raining now, you shouldn't leave until it stops raining.