Rain Dance is a Water-type move that changes the weather to rain for five turns. If the user is holding a Damp Rock, the rain will last eight turns.
The weather caused by Rain Dance is specific to the battle it is used in. The current weather in the Minecraft world has no bearing on the weather in battle and vice versa.
Rain increases the power of Water-type moves by 1.5× and decreases the power of Fire-type moves by 50%. SolarBeam's power is decreased to 50%, the moves Synthesis, Morning Sun, and Moonlight will recover ¼ HP, and the moves Thunder and Hurricane will always hit.