How Fall Weather Affects Your Roof

Your roof protects you from the elements. Day in, day out, the roofing system works overtime to keep your home’s exterior safe from water damage, maintaining its structural integrity. Sunny for several days in a row, then windy, then lower than seasonal temperatures at night – fall weather affects your roof in ways that you might not expect.


It might seem strange to find out that heat can affect a roof’s performance when you have to grab a light jacket even though the sun is shining. But the surface temperature of a roof, particularly one made of asphalt or is darker in colour, can rise significantly on a fall day if the sun shines directly on it for an hour or more.

Heat causes roofing materials such as asphalt and cedar shingles to expand and contract, possibly loosening nails and allowing moisture to get in behind roofing tiles. The sun can dry out roof shingles, causing them to shed the protective granules that help minimize UV exposure. This can lead to tiles becoming so brittle they crack or when they are not too dried out, they start to curl.


Humidity measures the amount of water vapour in the air. In Vancouver, the humidity ranges between 60 and 80 during the month of October. Humidity that is too high or remains at the high end of the index for several days in a row, can negatively impact a roofing system. When the surface of a roof becomes cooler than the surrounding air, condensation forms. While this is more of a danger in the summer months as humidity combines with high temperatures, excess water forming from humidity levels in the fall can still cause damage to insulation and encourage mold buildup.


Rain affects a roof on a regular basis, but the change in season from summer to fall can be dramatic. October weather has been especially mild but won’t stay that way particularly as we head toward November. While rain is not the immediate cause of the problems experienced by roofing systems, it can help make matters worse.

It’s important to inspect your roof if it’s over 15 years old. The older the roof, the more vulnerable it becomes to missing tiles, damaged tiles, roof deck warping, and rotting soffit and fascia. The heavier rainfall coming our way can attack weak areas of a roof, allowing water to collect, seeping into places such as the soffit, fascia, and decking, letting leaks, mold, etc. to form.


Yes, a windy fall day can certainly lift flashings, make a few loose roofing tiles disappear, and deposit debris onto the roof that blocks vents or ends up in the gutters. But it can also make trees come into contact with roof shingles. This doesn’t have to be as dire as a tree falling directly on the roof. Branches brushing across roofing tiles can remove the surface granules that protect the roof from UV and moisture damage. A windstorm can also cause branches to knock up against fascia or dent aluminum gutters.