94 C is the max temperature

https://www.geforce.com/hardware/desktop-gpus/geforce-gtx-1080/specifications

Clock start to reduce as the temperature goes up, but bigger drops comes in at 83c like the guy mentioned in reddit post.

https://www.reddit.com/r/nvidia/comments/4tju34/when_does_the_gtx1080_start_to_thermal_throttle/