>Weather Ball is unaffected by Normalize, Pixilate, Refrigerate, and Aerilate. ~ Bulbapedia
Weather Ball will be a Water-type move. This is because Weather Ball instantly changes type once weather goes up. So, when Mega Glalie uses it in the Rain, it is in fact using a Water-type move.
If there is no weather active, then Weather Ball is affected by Refrigerate because it stays a Normal-type move.