We have no snow in Washington, won't for a while. Changed my Christmas trip,
will be going to the Missoula area. Sledding in the Seely Lake, Lolo, Lincoln areas
among others. My question is when or do I have to rejet my sleds. We don't ride
above 5'000 ft in the areas I have been. ;)

There should be a chart available for your sled..

If you go to the dealer, they can copy a page from the manual. It will give you temp/alt settings. Just be careful when doing this if you are not accustomed to playing with your jetting!!
This is a copy from my 2000 Formula Z 700, I used it when I went to Montana/Idaho/wyoming.
FZ700

Here is the other sheet you would need, it has your pilot jet, needle jet and air screw, and alot of good info.
This is for my sled, do not go by my sheet!!
FZ700