Difficult to handle rain anytime but we never had any on the Boise or Cali trips. Of course you worry about breaking down.
The worst rain I ever had was a solo trip heading South to pick up my Wife in Daytona for a few weeks down South. Near Dunn, NC I had the worst rain breakdown ever. At that time I had installed my Soob Frankenmotor and very heavy rain came down for miles with no exits available. Plenty of rain came into the cabin, no where to pull off safely and suddenly I'm down to 3 cylinders running. I finally got off 95 and a Napa store put me in touch with a local hot rod shop who took me in and fixed things up. They filled the spark plug recesses with dielectric grease after drying things out properly. At one point I didn't even know what town I was in. Got a hotel room and started to dry things out. Had about 1/4" of water in the footwells, even had to put my shoes in a clothes dryer. It turned out that the louvered rear lid would collect rain water and that would overflow and flood the engine. Holes were drilled in the lid in Cocoa Beach.
RainX in and out helps some. A real good defroster helps too. Good wipers are a must. At that time mine had two speeds. Slow and slower.
Good planning and some flexibility in your schedule would be good too. I failed there.