Yeah, for most the Interstate is 80, by God, get out of my way! even in Noah rain.
I'll drop to 50 or even 45 when most folks are parking under the overpasses to wait it out. Rain like that is in squall lines, and if you park to wait for it, you'll be there 20 or 30 minutes, if you drive out of it, even creeping along, you'll be clear in 2 or 3 minutes.
The rain makes this situation worse: the person in the left lane won't move over till you get right on their bumper. They're not watching the mirror so they didn't notice you approach from a light-year away to right on them in 15 seconds, but if you stay safely back, they assume you're OK back there. They don't move until you crowd them. If you flash to ask for passing room, they get all pissed off about it and slow down, like flashing says, "Move, punk!" instead of, "Excuse me, please, I'd like by." Like I said, if it's raining hard, this is just worse, because they don't care that your new 225/50s pump enough water to reverse Niagara Falls, they know that their minivan is right at the edge of disaster at 50.
Cruise control wars are the best, rain or shine. It takes the soccer mom (Danoff is loving this stereotyping, I know

and I admit it's not EVERYBODY, but it's more than enough to definitely be a strange problem) 6 miles to pass a semi, and once she's clear, she SPEEDS UP to change lanes. WhyTF couldn't she speed up to make the pass?
BTW, I'm in Panama City, used to run Dixie Region Solo II (G-Stock Probe, black) every month in the mid to late 90s, and also Gulf Coast Region in Pensacola. I went to Wiregrass a couple of times, but not often. Bought a house, can't afford the tires any more. . .

Did you run there with us?