Over Thanksgiving a big storm blew through. We were out of town but I noted that my weather station reported a bunch of rain and then stopped transmitting. When we got home, I climbed up on the roof to investigate. I replaced the batteries (which hadn't been changed in 2.5 years) and the station started reporting again.
This guy hung out with me for a bit while I was replacing batteries and cleaning sensors:
However, next time it rained it stopped again. Then it dried up and started again. Then rained again, etc. So it was dying when wet. And the humidity reading was stuck at 99%. I tried all the troubleshooting procedures I could find but was unable to restore functionality.
So, I bought a new sensor array and installed it today. The new array is an upgraded design. It's easier to take apart and clean. They reduced the power requirements so it runs on 2 AA batteries instead of 3. And they added a super capacitor to the solar array so it can run off sunlight without pushing any current through the batteries (the previous version pushed the solar current through the batteries to both stabilize the power and trickle-charge the batteries).
So the my weather station is up and running again!