Hunted Iowa all of my life. Level B "minimum maintenance roads" are best left un traveled after any precip until either they dry out or freeze. If they're frozen and it is supposed to get 35 or above with sun you better make sure you're on them before that top layer thaws out, they turn into an ice rink.
There 100% are some roads in northern Iowa that can turn into a "no-go zone" when wet out. I made a mistake one time and I'll never forget it. There was a minimum maintenance sign, I drove past it, everything was fine, a little gravel here and there. This was a long road as I recall, maybe a section and a half or a little more. Long story short the gravel slowly gave way to a dirt road that was really an absolute grease track. I turned on 4 wheel and even locked the rear diff. but it didn't do much. I slid to the right and my tires caught on an oh so tiny lip, and I rode that thing for a mile straight and somehow it kept me on the road. I'd turn my front tires 90 degrees and the truck still went straight. My pucker factor was at 11 and I said a prayer when I got out of that mud pit. I've never looked at a dirt road the same way since!
Thanks for all the replies. Sounds like the minimum maintenance roads are much like western ks roads when wet. Best to avoid them till it dries out which probably won't take long as dry as everything is.