Get the local dirt/gravel road regraded. It works without fail every time for ours. They started regrading our road on Tuesday, completed yesterday and a storm came through overnight. We were meant to get 1-5mm of rain. We had over 21.0mm of rain, so almost an inch, and trees down because the re-grading changes the weight of soil & rocks on the roots of the trees growing in the verge.
Works without fail.
There are no gravel roads near me, so I have to resort to washing my car. For extra measure, I can wash it, clay bar it and wax it. The more work I put in, the higher the chance of rain.