It's snowing.

正在下雪。

It's snowing hard/heavily.

正在下大雪。

This snow won't last long.

这场雪下不长。

See how big the snow-flakes are!

瞧，雪花有多大！

I think there'll be a snow.

我想要下雪了。

Do you think it will snow?

你认为会下雪吗？

It's thawing.

雪在溶化了。

Is it snowing(or sleeting/hailing) ?

在下雪（或雨夹雪/下雹）吗？

We had a snow yesterday.

昨天下了一场雪。

In the South,summer is very hot and winter is mild with no snow at all.

在南方夏季炎热，冬季温和，根本不下雪。

In the North, summer is short and mild, while winter is long and cold with a good deal of snow.

在北方，夏季短，天气温和，冬季长，雪大严寒。