you have to catch or kill kyogre
There's no real reason, sometimes it rains, sometimes not.
You trade them in a house left of pastoria city. She gives you the TMs Hail, Sunny Day, Rain Dance, and Sandstorm depending on the 10 Shards you give her. Nothing else.
Pass the rain puddles and go to Route 8. Follow Route 8 to the Tubeline Bridge.
spring
Route 213
In pearl? Well, you can go to the Route that's west of Pastoria City, and in the middle of the route (closer to Pastoria) you can find a house. In there a person will trade you A TM Rain Dance for 10 Blue Shards. In Platinum it's a move tutoring item, and in RSE you trade em in for Rain Dance TMs just East of Lilycove.
Laverre City and the Route under it.
route 212 (rain) use the poke rader
In Pokemon Pearl, the TM for Rain Dance does not occur somewhere the player can find it. Instead, they must collect ten blue shards and trade them with the mountain guy outside of Pastoria City for the TM.
you have to catch or kill kyogre
There's no real reason, sometimes it rains, sometimes not.
you have different forms in what ever whether like rain dance sunny day and when its foggy
Get a groudon and the rest of the Pokemon doesn't matter. If you need to catch groudon talk to the guy who gave you catsformin the weather institude and he will tell you there is a drought or heavy rain on some route go to that route and there will be Groudon if there was a drought and kyoger if there is heavy rain.
it is on the abandoned ship near slateport city you need to have dive to be able to get it. it is in that one room where you have to dive down to get it. thanks, emerald lover and owner
ANSWER:you can't through normal play. You must dongle with FireRed in the DS and Ekans will appear on Route 212 (Rain) and Growlithe will appear on Route 201 & 202.
You can get rain dance on route 223