I am cold water WFP, but the 1st lot of snow I was working in -6 and had no problems, but on Friday last week it was -3 and water was freezing on windows.
Don't make sense I know, but it was also a very strong cold wind on the Friday, which i imagine caused it to freeze at lower temperature.
So its not just how cold it is, its also its other factors like the wind.
Darren