Rain Dance has 5 (max 8) PP. Source
Sunny Day has 5 (max 8) PP. Source
Hail has 10 (max 16) PP. Source
Sandstorm has 10 (max 16) PP, but does not change Castform's form. Source
The original PP for Rain Dance and Sunny Day is 5, but with PP Ups can be increased to 8. Hail and Sandstorm, otherwise, has a regular of 10 PP, but can be increased with PP Ups to 16. PP Maxes can also be used to quickly increase PP to the limit.