How to Get Sunny Day in "Pokemon LeafGreen"by Daniel ValladaresUpdated September 22, 2017
Sunny Day is a battle move in "Pokemon LeafGreen" that has three main advantages: it increases the power of Fire-type moves, it allows Pokemon to use the powerful move Solar Beam without having to wait a turn to recharge and it erases any other weather effects that are going in the battle. In "Pokemon LeafGreen," Sunny Day is found in the Safari Zone in Fuschia City. To obtain Sunny Day, you will need a Pokemon that knows the move Surf.
Travel to Fuschia City and enter the Safari Zone.
Pay $200 to play the Safari Zone game. Make sure you have a Pokemon with Surf in your party.
Travel to the second area of the Safari Zone and use Surf to cross the body of water. Pick up the item on the island. It will contain TM11, which allows you to teach Sunny Day to a Pokemon.
Pokemon that you can teach Sunny Day to are Charizard, Rapidash, Magmar and Flareon.
Other items in the Safari Zone include TM47, TM32 and a Leaf Stone.
These steps also apply to "Pokemon FireRed."
Once you use a TM on a Pokemon, it disappears; choose wisely before using Sunny Day on any Pokemon.