Rain is called by the move Rain Dance and the ability Drizzle, and is the most common naturally occurring weather condition. It increases the power of Water-type moves by 50%, and decreases the power of Fire-type moves by the same amount. It prevents Thunder and Hurricane missing. On the other hand, it causes Solar Beam to only deal half of its normal damage, and lowers HP recovered from Moonlight, Synthesis, and Morning Sun to ¼ of max HP. It is associated with the abilities Dry Skin, Hydration, Rain Dish, and Swift Swim.
>Rain turns Castform into a Water-type and changes Weather Ball to a Water-type move and
doubles its power. Sliggoo evolves into Goodra starting at level 50 when leveled up during rain in the overworld.
Source
