Iam behind in cutting my joints and would like to put up my sauna next spring is there a problem cutting joints in the winter when my timbers will be frozen.

The will be a bit harder to cut due to the fact that the wood is frozen.

Jim Rogers

From my experience of working in a unheated shop through many winters, frozen timbers are rarely a problem, it needs to be very cold for them to be difficult to work. Most of the time they are no different than warm timber. extended temps in the single number can have a effect on workability but doable. The bigger factor is snow and ice built up on timber left outside to be brought into the shop and having to chip ice off or out of mortises. Cover them the best you can, keep them separated from each other, they will stick together.