Really we need a local entomologist, there is also the possibility they fly if disturbed even the the temps are lower.Connecticut
They emerge in late November to December.
[..] They fly when temperatures are above freezing ..
A native moth called the Bruce spanworm has an identical biology and development to the winter moth. These two species are able to mate and produce offspring.
only iffy bit is it was below freezing in Cornwall that day from 6 pm on.