Protect the things that must stay dry
Put bedding and spare clothing in suitable waterproof bags or liners. Keep wet footwear and outer layers away from them. A backpack cover may help with showers, but it is not the same as waterproof storage for everything inside.
Plan a wet arrival
Keep the tent and rain clothing where you can reach them without emptying the car. Know the pitching sequence in advance. A small towel near the entrance and a separate bag for wet items help contain the mess. Do not cook inside the tent or an enclosed shelter.
A repeatable kit means less to remember next time.
Make changing plans easy
Pack a ready-to-eat meal and a low-key activity. Check current campground notices and forecasts before departure and while connected. Heavy rain, flooding or severe weather may call for delaying or ending a trip; the ability to leave comfortably is part of good preparation.