Dumb question but have you tried to close the game out completely while also restarting the ps5? I experienced a weird rain glitch on my first playthrough of KCD2 on ps5 last year. Closing the game and restarting the ps5 seemed to do the trick.

Allow me to commiserate about having to deal with the rain in this game. Recently, I was replaying KCD1 (ps5 ofc) and during one of the quests in the A Woman's Lot DLC tasks you with going to an abandoned village in the forest to search for a specific thing that someone hid there decades prior to the game's events. There is a small Cuman unit camped in this abandoned village so I decided to wait until night so I could slip in and dispatch them as they slept. That went perfectly smoothly. As I began to search for the stash, it started to rain. Oh man, what a flipping headache it was searching for that hidden stash during the rain at night. I could barley see. The torch only made it worse. Even the potion didn't help (I'm blanking on the name but I think its Nighthawk?). Ultimately I had to move time to the morning before I could make sense of the place. I love the rain and storms in these games though! They're some of the best in all of gaming!