Airpod Pro dieing quickly in sauna?

Just got my airpods for Christmas and I love them! However I've noticed that when I'm in the sauna, they seem to die after only 2 hours of use on a full battery. It usually starts with the left airpod dieing first (the side that's closest to the sauna) followed by the right airpod. When I put them back in the charging case, it shows that they still have around 40% battery. Are my airpods automatically turning off due to the excessive heat? The temperature in the sauna is usually around 145F.

TLDR: Airpods turn off after about 45 mins in 145F sauna, but when I put them back into the charging case they still have 40% battery. Defective pair or just too hot in the sauna to use them?

Thanks!