...
P.P.S. Note that with low overcast skies, the radiation error will be small anyway, so these data still can be used.
P.P.P.S. Now that it has been several hours since the rain ended, I tried a reset (^R) again. This time, the fan is back at about 38mA and stayed up. Also, I didn't see much of a change (if any) in temperature after it restarted. So...we might say that it was just the rain and now works, but I'm still suspicious.