Below 4°C. That’s the threshold for asphalt shingles. Drop below that and the shingles get brittle, crack during handling, and the heat-activated adhesive strip stops bonding properly. The result is a roof that’s vulnerable to wind lift and water infiltration right from installation.
Most Ontario roofing contractors handle cold snaps one of two ways. They either pause the job or hand-seal each shingle with roofing cement when temperatures are borderline. Winter roofing in Windsor is doable during mild stretches but it takes experienced crews and it adds labour time and material waste to the project. If your roof is failing in January and you can’t wait, make sure your contractor has a cold-weather protocol and that the manufacturer warranty covers the temperature conditions the installation is happening in.
Temperature constraints are a big part of why the best time of year to replace a roof is late spring or early fall. Consistent temps above 10°C give the adhesive the best shot at sealing properly. Cold-weather installs also increase labour costs, which feeds into what the most expensive part of replacing a roof ends up being when site conditions aren’t ideal. For a full cost picture see how much it costs to replace a 2,000 sq ft roof in Ontario.