Does Victoria get less rain than Vancouver?

The rain shadow is strongest over the south-facing core: Fairfield, James Bay, Oak Bay and the Gonzales hill itself, which is why the city station is the dry one. Moving north and west the shadow weakens; the UVic station in Gordon Head records about 661 mm, the airport in North Saanich roughly 45% more than the city, and Sooke and the Highlands more still. A Metchosin roof lives in a wetter, windier and shadier climate than an Oak Bay roof twenty kilometres away.

That spread matters more to roofers than the Vancouver comparison. In Sidney and along the Cordova Bay waterfront the issues are wind and salt on a sunny, quick-drying roof; in Broadmead and the Highlands they are shade, needle drop and moss under trees. The dry core is where asphalt lasts longest, and where Vancouver-style advice about 'the wettest climate in Canada' least applies.

Pacific storms arrive from the southwest carrying moisture. The Olympic Mountains across the strait force that air up, it cools, and much of the moisture falls on the Olympic Peninsula. What crosses the water to the southern tip of Vancouver Island is drier, and the effect is strongest directly in the lee, which is the Victoria core. Vancouver, to the northeast, sits under the flow that goes around the mountains and then hits the Coast Mountains, so it gets the full load.

The shadow fades with distance. By the Malahat and Sooke the totals climb back toward typical coastal values, which is why Greater Victoria has such different roofing microclimates within a half-hour drive.

Less rain does not mean an easier winter for shingles. Victoria's wet season is as long as Vancouver's, roughly October to April, and its winters are just as mild and humid; there is simply less water in each front. Roofs in shade stay damp for the same months, moss grows the same way, and a north slope under a Douglas fir in Saanich behaves much like one in Burnaby.

Where the difference shows is on roofs that get sun and wind. Those dry between fronts, moss struggles to establish, and asphalt reaches the top of its local lifespan. It also shows in summer: Victoria's July and August are nearly rainless, giving roofers a long, reliable window that Vancouver crews envy.

Much of the 'best roof for a rainy climate' content online is written for Vancouver, Seattle or the outer coast. Read it with three adjustments for Greater Victoria.

• Discount arguments based purely on rain volume; the driver here is shade and moss, so ask where the trees are before asking about rain
• Keep the arguments about ventilation, ice-and-water membrane in valleys and new flashing; those are about damp, and Victoria is damp
• Treat wind and salt as the coastal factor on exposed sites, and specify metal and fasteners for it
• Expect a longer dry season for scheduling, and book it early