OK, so our own projects always come last after getting the ones that pay the bills complete. As I have stated before I am not a roofer, so I am asking the question to those who specialize. I have 2 sections of roof to complete, witer has finally hit here in NH, one is on the north side of the house a couple hours of work, but the frost stays on the underlayment all day, I would prefer to shingle it without the frost undernieth, but if Ishingle over it(frost) will this cause me long term problems, in which case I may as well just tarp and wait for a really warm day? The roof literallygets no sun at this time of year. Being well ventilated it does not heat up much to speak of either.