Advertise an interior detailing service.
Forget it. I work at a car wash and for us rainy days are our work days, when we do maintenance that we can t do when we re open. You ll always have a few stupid people who want to come through, but it s just easier to close and get stuff done.
You could set up a car washing center with a bay and easily make money.
tell the the rain damages the paint work n they need a wax to get the shine back