In the snowy biome weather_at_position is not updated with the sensor
Steps:
Generate a world with the seed 933362424
activate the addon that is attached to the report
make it rain activate the /weather command
as expected: update labels in rain state
What happens: the label is not updated state
Snow is not rain. The weather_at_position filter checks the actual weather, not the current global weather setting.
Have you tested whether weather_at_position can return "snow" as a value? If it doesn't, you may be able to test for that by using a combination of "weather" and "is_snow_covered" and "is_underground".