A lot depends on temperature. Cold and raining is a lot worse that warm and raining. in warmer weather they will dry out faster, obviously. 1" of rain is probably somewhat equivalent to you watering them. 3-4-5-6" of rain is too much.
How about a tarp type lean-to over them? I would find someway to minimize the impact if it is going to be an issue. Maybe picnic benches, strips of wood and a tarp. Time to get creative and think outside of the box.