"When no weather condition is under effect, Weather Ball deals Normal-type damage. During any weather condition, Weather Ball attacks with a different type and its base power doubles to 100. The type that Weather Ball is depends on the weather conditions at the time it is used. It will be:
* Fire-type if it is sunny.
* Water-type if it is raining.
* Ice-type if it is hailing.
* Rock-type if there is a sandstorm.
* Normal-type if it is foggy or there is no special weather condition in effect.
* ???-type if Shadow Sky is under effect.
Type power-ups from the weather will be put into effect, as well as STAB caused by Castform's type changing from its ability, Forecast. "