why can't the engine start after a heavy rain?

What is your question?

I have a toyota rav 4,1996 with three doors.When it has been raining heavily (the car was parked somewhere under the rain), the engine can't start and when the sun rises (some hours later) the engine starts. my anticipated thanks for your help.

What makes this problem better or worse?

If on saturday i did'nt go anywhere with it and it's raining on sunday, on monday it's worse.