Since the games run on the same engine as the Ruby and Sapphire (and, by extension, Emerald) games, the same weather effects are also in the data for both versions. These include Cloudy, Rain, Snow, Thunderstorm, Sandstorm, Volcanic Ash, Mist and even a texture for Underwater. Except for the cloudy and Mist weather effects, all others are unused.
Contributed by gamemaster1991