Any frost-free season works - but each has a case
House washing in Southwestern Ontario runs from early spring through late fall; what matters most is not the month but the cadence - most homes need a wash every 1-2 years before buildup takes hold.
Spring is the reset: it clears the salt spray, sand, and winter grime off siding and concrete, and preps the exterior for the season you actually use it. Early summer is when the humidity-driven algae and mildew hit their growth stride, so a wash then knocks growth back at its peak. Fall is the strategic clean: removing organic material before winter means it is not feeding under snow cover for four months.
Why this region is hard on exteriors
Southwestern Ontario combines two enemies of clean siding: humid summers that feed algae, mold, and mildew on any shaded elevation, and salt-heavy winters that coat everything near a road or driveway. North-facing walls and tree-shaded sections green up first - if you see it there, the rest of the house is next.
Timing around projects and events
Some dates make the decision for you. Selling? Wash before the listing photos - a clean exterior is one of the cheapest improvements to how a home shows online. Staining the deck? The wood-safe wash comes first, always. Hosting a graduation, wedding, or backyard season? Book a few weeks ahead; summer slots fill fastest.
The one season to avoid is deep winter: soft-wash solutions and rinse water do not behave below freezing, which is why the season runs spring through late fall.
