Back to silly requests.
How about this?
[spoiler][/spoiler]
It is simple but it doesn't make it easy. We need ridiculous flying speed, an ability to survive an occassional crash, and some weird weather-related special abilities. (such as physically moving clouds or stomping them to make rain/thunder)
Awakened Winged Horse with Access to control weather (and other weather spells) and prestidigitation (for the colors)?
Has 2 LA and 5 HD, 80 ft. move speed, and can still get 7th level spells.
Crash survival can be done with the indominability spell (if would be reduced below 1 hp, is instead reduced to 1)
If you don't mind losing 20 ft. of speed, go pony for only 4 HD.
Glove of man allow for use of hoofs as hands.
EDIT:with Fly like an arrow from dragon 308, run, The speed doubling from rapid wrath, and maybe another boost, we can reach 6760 ft speed, which is over Mach 1. (light horse would reach 8000 ft. without anything unlisted, pony would need a source of + 10 ft. speed which I'm pretty sure items can do.)
EDIT 2: Combine with dive for 16000 ft. move going down (12000 on a pony).