Saw these single-fingered mittens on people that took my flight up to Canada.  It was about 20 BELOW 0...and that was WITHOUT the wind chill factor.  So I guess THESE are the mittens to have!!!!!
{"Image ImageDescription": "One-finger mitten aviator gloves, circa 1943-1945, made of leather, fur and wool.", "Image Artist": "San Diego Air and Space Museum"}