You can install
https://github.com/weewx/weewx/wiki/mqtt and subscribe to e.g. weather/loop (or whatever your topic is) and extract windSpeed. You will receive windSpeed every time your hardware send loop data to weewx. With my WS-2810 this would be about every 3 seconds, my weatherflow tempest provides windSpeed every 3 seconds. Your switching device need to be mqtt enabled, you need a broker as well.
Other than that there are several other ways to let weewx do something when specific loop data arrives.