🧂 Road salt and sand at every entry point

Calcium chloride (the deicer used across Montreal’s streets and sidewalks since the 1990s) is highly hygroscopic — it attracts moisture and stays active on surfaces long after the shoe that carried it in has moved on. On hardwood floors, calcium chloride residue causes long-term finish dulling and, in high concentrations, actual wood swelling at the grain level. On carpets, the combined salt/sand mixture is abrasive: every footstep after entry grinds these particles against the carpet fibres from below. The white residue visible at entry points is the symptom; the fibre damage happening invisibly deeper in is the real cost.

→ What to do: Weekly damp-mop of all hard floor entry zones with a pH-neutral solution. Vacuum entry carpets and mats twice a week minimum from November to April.

🌬️ Forced-air heating and concentrated indoor particulate

When the heat comes on in October and stays on until April, the forced-air system becomes a continuous distributor of whatever is in the air — dust, skin cells, pet dander, mould spores, bacteria. Furnace filters capture some of this, but the horizontal surfaces that receive the distributed fine particulate — tops of door frames, ceiling fan blades, window ledges, the backs of furniture — accumulate visibly faster in winter than in any other season. Dusting frequency should increase from monthly to bi-weekly between December and March.

→ What to do: Change furnace filter every 2 months. Include top-surface dusting in every cleaning visit from December to March.

💧 Bathroom humidity and mould window

Winter in a well-sealed Montreal home concentrates bathroom humidity: hot showers in an enclosed, poorly ventilated space produce condensation on every surface, and the temperature differential between interior bathroom air and the exterior wall drives that moisture into wall joints and grout. The two to four weeks after the heat turns on in October — before occupants have re-established ventilation habits — are when bathroom mould colonization typically begins. January and February, when the home is at its most sealed, are when it accelerates.

→ What to do: Monthly grout scrubbing throughout winter. Exhaust fan after every shower for minimum 20 minutes.

🌸 May–June: Pollen peak on every horizontal surface

Montreal’s tree pollen season (birch, maple, oak) peaks from late April to mid-June. Every open window deposits fine yellow-green pollen on windowsills, counters, floors, and upholstery. For allergy sufferers, this is the most symptomatic period — and the one where HEPA vacuuming and surface wiping needs to increase in frequency to reduce indoor allergen load. Weekly dusting of all horizontal surfaces is the minimum from May to mid-June.

🌡️ July–August: Humidity and kitchen bacterial peak

High summer humidity dramatically accelerates bacterial growth on kitchen surfaces — particularly the areas that are never quite dry: the sponge, the sink drain, the rubber seal around the refrigerator door, the bottom of the dish rack. These zones need weekly targeted disinfection throughout July and August. Bathroom mould also re-activates in high humidity even in well-maintained homes — grout scrubbing should resume monthly from July.

🌿 August–September: Ragweed — Montreal’s most aggressive allergen

Ragweed pollen season begins in mid-August and runs through September — and Montreal is one of the most ragweed-affected cities in Canada. Unlike tree pollen, ragweed pollen is so fine it penetrates window screens and is distributed by the slightest air movement. For the 20–25% of the population with ragweed sensitivity, indoor surface cleaning frequency from mid-August through September is as important as any other period of the year.