My anemometer is frozen right now also. I usually just wait for it to thaw naturally.
You could put a heat lamp or flood light on it to thaw it - don’t know how you would do anything preventative though.
I have let mine thaw out as well. but you can always experiment. One board suggested using heat tape, but the next thought was that maybe the heat tape might damage the plastic or even produce a magnetic field that would mess up the reed switch. Another person suggested spending 4 thousand dollars and buying a professional one. We haven’t heard much from him lately since that incident.
Another did suggest a light bulb near the unit , red was the color … one it would put out the heat as necessary and two freak out the neighbors with the red color - making them think it was to scare off aircraft that might hit the thing.
Someone also suggested an aquarium heater.
I think you have to experiment and let others know what works. The thing is make of plastic, so the bulb or heating has to be just enough to melt the ice and cool enough to protect the unit. I think this is where the fun is in this hobby … problem solving to make things work like we want them to.
Had a thought… A stupid one , but put an umbrella over the top of the unit so that it is high enough for the precip to hit the umbrella, but so the umbrella doesn’t interfer with the wind instruments.
Now watch someone will invent it and make a mint. Rats.