Last Thursday I think I set a personnal best. I have painted in temperatures as low as 20 degrees but Thursday it was 15 degrees when I started. The biggest issue was the thickening of the Titanium white. It needed liberal doses of terp to perform properly. Also, 15 degrees is not too cold for muskrats. I had a couple that were swimming the river back and forth about 10 feet in front of me the whole time I painted. I am not sure what muskrats have to do that would make them so busy, but they were getting it done.