The only reliable way to predict the weather is to use the Weathermage.
This is a mage who's only job is to camp a region and monitor the weather conditions.
Checking in with your Weathermage when logging in and logging out are good times to begin and end a day of wow. Be sure to check your mid-day report and any other times you feel the Weathermage might have news for you.
My Weathermage has been of great service in collecting pets where the weather on the ground is of critical importance.
The arctic foxling took almost 2 weeks of steady weather watching before snow began falling and the foxes came out to play.
Good luck with your weather watching.