ask your mom

Just keep going back that's what I did to get Articuno.

Rayquaza
Level: 45
Size: 4
Friend Area: Stratos Lookout (Automatic)
Location: Sky Tower Summit 9F (through Sky Tower 25F)
Recruit %: -10%
Other Requirements: Must complete story mode. Note the negative recruit percentage, you will need high level Pokemon and/or Friend Bow in order to have a chance to recruit it.



Rayquaza / 10% / Sky Tower Mid 9F





Recruiting Groudon & Rayquaza
First of all, make sure that you come with only one Pokemon of size 1. Rayquaza and Groudon are size 5, I believe, so you can only have one Pokemon. Also, their base recruitment rate is -10%. Therefore, I suggest coming at a high level, with the Friend Bow as a hold item (boosts recruitment chances by 10%). With the Friend Bow, you can recruit them at as low as Level 30, but the chances are minuscule. I would wait until around level 80+, so you have at least a 10% chance of recruitment.




RAYQUAZA:

You can't recruit him till you beat him once. His Dragon/Flying combo opens him up to Ice. His-10% recruit does NOT help, but you can use the Mid Method here!