The main issue is shingle sealing
Asphalt shingles have a strip of sealant that bonds each course to the one below. The sun warms it and it sticks. In cold weather it may not seal until spring, which leaves new shingles more open to wind lifting them in the meantime.
Manufacturers publish cold-weather installation instructions for this. They often call for hand-applying dabs of roofing cement under the tabs, storing bundles somewhere warm until they go up, and taking extra care because cold shingles crack more easily when bent over a ridge or into a valley.
Fewer working days
Crews need dry decks, so snow, ice and frost on the roof push start times back on winter mornings, and short days end them early. A job that takes one or two days in June can stretch over more in January. Tear-offs are planned so the house is never left open overnight.
- Ask what the crew does if weather turns while the old roof is off.
- Ask how they handle frost on the deck in the morning.
- Make sure the contract says who protects landscaping and walkways from ice and debris.
Materials that care less about the cold
Metal roofing is fastened mechanically and does not rely on a sealant strip, so winter affects it less. Slate is the same. Flat roof membranes vary: some need warm temperatures for adhesives or seams, others are mechanically fastened. See slate and metal roofs and flat roofs on rowhouses.
When winter work makes sense
If the roof is leaking, waiting until April is often worse than a careful winter job. Water in insulation and drywall through a season of freeze and thaw does its own damage. If the roof is old but dry, many homeowners book for early spring and use the winter to sort out the attic.
Ice at the eaves
A winter replacement is a good time to make sure the ice barrier at the eaves is done right. See ice dams on Harrisburg-area homes.
Questions
+Is there a temperature below which shingles should not be installed?
Manufacturers set their own limits and cold-weather steps. Ask the roofer which product they are using and what its instructions say for cold weather.
+Will winter shingles seal eventually?
Usually, once warm sunny days arrive. Hand-sealing during installation covers the gap until then.
+Does a winter roof job need a different permit?
No. Any permit rules are the same year-round. See [Pennsylvania roof permits](/questions/pa-roof-replacement-permits).