We didn't go for a walk in the mountains because ... very foggy.
it was
... a lot of clouds, so we couldn't see the sun.
There were
... some snow, so we could ski!
There was
... dangerous for boats yesterday because ... a big storm at sea.
It was, there was
... a wonderful sunny day, so we all went to the beach. ... some people we knew there.
It was, There were
I took my umbrella because ... rainy outside.
it was
The treez were moving because ... windy.
it was
... really cold! ... ice on the windows!
It was, There was