Kept my hands warm in 18 degree weather and I fished for 5 hours!
As I mentioned in the below post, I got to try out the Simms wind stopper fold over mitten today. The temperature was 18 degrees when I started fishing and these gloves preformed amazingly. I like that you have a mitten part and also a separate fold over for your thumb. It also comes with elastic bands so you can fold over the mitten and it won't get in your way. They were surprisingly water proof as well. I highly recommend these for the winter fisherman.