要下雨了。

It is going to rain.

因为要下雨了。

Because it's going to rain.

我觉得要下雨了。

I think it's going to rain.

天气似乎是要下雨了。

The weather seems to be about to rain.

天空看起来要下雨了。

The sky looks like it's going to rain.

天空变得黧黑，要下雨了。

The sky turned dark, and it was about to rain.

天空变得晦暗，好像要下雨了。

The sky turned dark and gloomy, as if it was going to rain.

天空乌云密布，看起来要下雨了。

The sky clouded over, it looks like it's going to rain.

天空变得阴沉，看起来要下雨了。

The sky has become cloudy, it looks like it's going to rain.

你最好带把伞，看起来要下雨了。

You'd better bring an umbrella, it looks like rain.