Pollen Count & Forecast for Yokohama

Yokohama’s spring allergy season (February-May) is dominated by Cedar and Cypress pollen; Japanese Cedar (Cryptomeria japonica) prolific in the Tanzawa Mountains and Kanagawa hills; Japanese Cypress (Chamaecyparis obtusa) common in Negishi Forest Park. Summer (May-August) sees high Grass (Poaceae) pollen levels, originating from the Tsurumi River banks. Autumn (September-October) brings Ragweed (Ambrosia) and Mugwort (Artemisia) from areas near the Tama River.

Hilly terrain and coastal winds create variable pollen concentrations; humid air traps allergens in narrow residential valleys. Late summer and autumn see elevated Mould (Alternaria, Cladosporium) counts, from leaf litter in Sankeien Garden and damp urban canals.