There is every sign of rain.

It is threatening to rain.

The sky looks threatening.

It looks as if it is going to rain.

From the look of the sky, it may rain in the afternoon.

Judging from the look of the sky, we might have a shower before nightfall.

It looks like rain. You'd better take an umbrella with you.

It seems like the coming weather will be rainy.

It looks like it's going to rain.