Pollen Count & Forecast for Toronto

Toronto’s spring allergy season (April-June) is dominated by Maple and Oak pollen; Silver Maple (Acer saccharinum) prolific in High Park and the Don Valley; Oak (Quercus) and Birch (Betula) widespread in Rosedale. Summer (June-July) sees high Grass (Poaceae) pollen levels, originating from the Humber River banks. Late summer is dominated by Ragweed (Ambrosia); this is heavy along the Leslie Street Spit and rail corridors.

The city’s ravine system acts as a corridor for allergens; lake breezes from Lake Ontario can trap pollen against the Scarborough Bluffs. Autumn sees high Mould (Alternaria, Cladosporium) counts; these spores come from decaying foliage in Rouge National Urban Park and damp urban ravines.