I live in the rainy northwest. It’s hard to keep your truck clean when it’s sunny for a day, rainy for two, sunny for 1 etc etc. what I do is when I have been driving in the rain in a clean truck, when I get to my destination, preferably home, I hose off the entire truck. This replaces the dirty water that once dries, would leave it filthy, with clean water and if it clears up overnight you’re golden! If it dries up before you get to a hose this doesn’t work and you’re S.O.L. I just now went for a burn to get some cold buds and it’s pouring out. So here I am in the dark and the rain hosing down the beast. I’ll thank myself in the morning!