Low Fps when high in the mountains

I get about 60 fps below the mountains but when I go to the top, I get around 30-40fps. I've noticed the higher I go up the more lag. Please fix this.

Steps to Reproduce:
1. Go high into the mountains on creative
2. Fly around
3. You start getting really low fps

Observed Results:
The higher you go and faster you go, the game starts lagging a lot even on powerful computers. And if it starts snowing, it lags even more!

Expected Results:
No lag. Fps should stay at around what your device normally gets.