It rains vs it's raining

[towcats1]

Dear Teachers
If it rains tomorrow , we won't go out.
If it's raining tomorrow , we won't go out.
How many differences are there ? Which one should I take when I'm talking about tomorrow's weather?

 

[Tdol]

I'd use the second if you want to refer to a specific time- you are planning something at 3pm, say, and if it's raining then, you won't go out.