I'm on the wet coast and I intentionally ride in everything except snow. Riding in that isn't intentional. I've fab'd up a stainless mud guard that extends another 4-6 inches beyond the front fender. It helps a ton in the rain. I still get soaked but I no longer have grit on my pant legs when I get home. The advice given earlier is spot on. Ride even more defensively. Slow down on corners and an avoid slippery things like paint, leaves and the oil covered center section of each lane.

I don't have any shots of it right now. It was one of those things that I did at the end of a work day when we were having a biblical downpour. I felt I'd had enough and took a scrap of sheet metal, put two 90* bends in it for the sides and drilled a couple holes through it and the fender. Then I pulled out a scrap of 1/8" neoprene foam that we had kicking around and sandwiched that in between. It ain't pretty, but it works.

Theres a RR track that crosses a Busy road in TYler,, It crosses in a curve, a 45 MPH curve where most people are running 50. NOT knowing its there & running up on it in the rain could literally be a mans downfall,,
& the asphalt gap is kinda wide, too, probably 4 inches, so, its a bike crash waiting to happen, especially in wet..