Weather Property CoolWeather Auto
If GetCurrentWeather() == CoolWeather
;do some cool stuff
Something else you can do is use a magic effect, and have conditions on the spell the magic effect is attached to. This checks for the condition every second, but in a far, far less taxing way then via script. IF you can use this method, and it's an alternative to a lot of polling, often, I recommend using the MGEF method.