Whenever the wind gusts over 20mph I would tend to get tons of false rain reports on perfectly sunny days. I had strapped my PVC pole to a steel fence rod thinking that was sufficient. Apparently, the micro-vibrations caused by the high winds were setting off the haptic sensor.
So, today I’ve modified my setup by filling the 1" PVC pole with sand, and then placing that pole inside a 2’ long section of 4" pipe which is also filled with sand. There are a few inches of sand at the bottom, so the 1" pole never makes contact with anything other than sand.
The whole thing weighs quite a bit - probably 20+ lbs. The additional mass of the 1" pole causes it to sway a lot more, but low-frequency swaying of an inch or so doesn’t seem to be any problem. Hopefully, this will solve the high frequency vibrations and stop setting off the rain sensor every time the wind blows hard. I’ll report back in a week or so with the result of the test.