Best Time of Year to Replace Windows in Ontario

Ask ten people when to replace windows and most will say “spring” or “definitely not winter.” After more than 20 years installing windows through every month of the Ontario calendar, we can tell you the answer is more useful than that. Every season has a real trade-off, and the best time for you depends on whether you care most about price, scheduling, comfort during the install, or catching a rebate deadline.

The Quick Answer

For the best combination of price, availability, and weather, late fall through late winter is the sweet spot most homeowners overlook. Demand drops, crews are available within weeks rather than months, and modern materials install fine in the cold. Spring and early summer are the most comfortable but the busiest and, often, the most expensive. If you have failed windows, the right time is now; waiting a season costs you in heating or cooling.

Spring (April to June)

Pros: mild temperatures, easy caulking and foam curing, long days, and you’re done before summer heat. Cons: everyone else has the same idea. It’s peak season for every window company in Ontario, which means the longest lead times, the least scheduling flexibility, and the least incentive for anyone to sharpen a price. Spring rain also causes reschedules; exterior sealing needs a dry surface.

Summer (July to August)

Pros: reliable weather, fast curing, and kids are out of school if you want to be home. Cons: still busy, and you’ll be running the air conditioner with openings in the wall. Heat and humidity are less of a problem than cold for the install itself, but a full-house job in a July heat wave is uncomfortable for everyone. Dark vinyl frames are also at their most expanded, which a good installer accounts for when setting clearances.

Fall (September to November)

Pros: arguably the best installation weather of the year: cool, dry, and stable. Getting new windows in before the heating season means you see the savings immediately. Demand starts to ease after Thanksgiving. Cons: early fall is still busy because so many people want to be “done before winter,” so lead times in September can be as long as spring. Book in summer for an October install, or accept a November date, which is usually easier to get.

Winter (December to March)

Pros: the shortest lead times of the year, the most scheduling flexibility, and the best chance of a sharper price, since manufacturers and installers both want to keep crews busy. You also find every draft immediately; there’s no better time to see the difference. Cons: cold rooms for an hour or two per window, weather days that push the schedule, and the need for cold-rated materials and an experienced crew. Snow on the ground makes exterior access slower.

How Winter Installs Actually Work

• One window at a time. The old unit comes out, the new one goes in, the opening is sealed, and only then does the next window come out. A single opening is exposed for well under an hour. Your furnace keeps up; the rest of the house barely notices.
• Cold-rated foam and sealant. Standard latex caulk needs about 5°C or warmer. Professional-grade polyurethane and hybrid sealants used in Canada are rated for application at −18°C and some as low as −30°C, as long as the cartridge itself is kept warm. The same goes for low-expansion window foam; installers keep it in a heated truck and use winter formulas.
• Dry, clean surfaces. Sealant won’t bond to frost or wet brick. Crews wipe and warm the substrate, and a snowstorm or freezing rain day gets rescheduled rather than pushed through.
• Doors closed, rooms isolated. The work room is closed off from the rest of the house, floors are protected, and heat is kept on.
• Vinyl clearances set for the cold. Frames are at their smallest in winter, so a good installer leaves the correct gap for summer expansion.

Two things genuinely don’t happen in a deep freeze: exterior painting of wood trim, and stucco or masonry repairs. If your job involves those, they get scheduled for a thaw.

Lead Times: The Part Everyone Forgets

Replacement windows are made to order. From the day you sign, the manufacturer typically needs 4 to 8 weeks to build them, longer in peak season or for custom colours and shapes. Then the installer needs a slot. In spring, that can add up to 10 to 14 weeks from signing to installation. In winter, it can be 4 to 6 weeks total. So a homeowner who calls in April for “spring windows” is often getting July windows, while a homeowner who calls in November is often installed before Christmas.

If you want a specific season, work backwards: sign in January or February for an April install, sign in July for an October install.

Rebate Timing in 2026

This year there’s an extra reason to think about timing. Ontario’s Home Renovation Savings Program, which pays $100 per opening for ENERGY STAR® windows and doors installed as part of a bundle with a home energy assessment, is currently funded through late November 2026 according to program guidance, with nothing yet announced beyond that. The pre-retrofit assessment has to happen before any work starts. If you want the rebate on a 2026 project, book the assessment now and plan for a fall install. Details are in our 2026 rebate guide.

So When Should You Book?

Our honest recommendation for most homeowners in London and the GTA: get your quote in the fall, and let the installer schedule you into the first available winter slot. You’ll pay less, wait less, and spend the coldest months behind new glass instead of old.

WideView Contracting

A family-owned business that supplies and installs high-quality windows and doors throughout Mississauga, Oakville, London, and surrounding areas in Ontario. Over 20 years of experience and a reputation built entirely on customer referrals.