Look at how wrong I was.
It was an absolute downpour. But all was not lost!
The first session was mildly moist. We went out on slick tires since the sun was out and things were drying out. It was my first time on slicks in the wet and boy was it slippery. I have newfound respect for Formula 1 drivers who hold out through wet conditions on slicks. A dry line started forming in most corners, though, and it became faster and faster to stop using the rain lines.
Then the track dried out nearly completely. There were a few scattered patches of light dampness, but it was not in any critical spots. In the 2nd session I set the fastest time of the day, 55.9 seconds, which, considering that I haven't driven in 6 months, and the track was totally green and cold, is kind of impressive.
Then the rain came back. And it let loose a pretty good shower. It got everything wet enough for rain tires, and kept a heavy sprinkle going. Rain lines came into full effect, and I struggled. My entrances were fine, but I kept apexing too early and as soon as I started hard cornering on the rubber line it would just suck me into a vicious traction loss slide that is difficult to overcome at best. I spun a couple times at the exit of tic-tac-toe just trying to put too much power down in the wrong place with too much lateral load on the tires. Our times were a good 20 seconds slower than a good warm day.
A technical malady popped up with all the karts, and mine went first. As I was exiting the pits after a damage inspection from spinning off into the dirt, my engine cut out. I re-fired it and realized that it was missing heavily. I took the half a lap to circle around to the pits. Turned out to be a simple fix in the form of a new spark plug. We were not spending enough time at full throttle and these engines hate that. The karts all started feeling and sounding much healthier after the service (which took all of 30 seconds, since the spark plug is right on top).
Then the vicious clouds really let us have it for the fourth session. It felt like a monsoon. I decided to use the rain oversuit, which made me look humongous since I was wearing my normal impact suit underneath. Kept me very dry though (my hands still got rather waterlogged).
In the fourth session the rain lines needed to be hugely exaggerated. At some points we were almost running a high-side dirt line. My turn-ins for a number of corners were just a few inches from running out of road. Forget simply staying off the rubber line, if you weren't in the marbles, you had zero traction.
Nevertheless, my times improved over the more tame 3rd session. My fastest monsoon time was a 1:13.2.
Still, my kart control got a real workout and I'm sure it helped me overall. I learned a bunch more on racing in the rain. In California, every second of rain time is precious. We just don't get a lot here, at least during racing season. It was fun, too.