Pollen Count & Forecast for San Jose

San Jose’s spring allergy season (February-May) is dominated by Oak and Sycamore pollen; Coast Live Oak (Quercus agrifolia) dense in Alum Rock Park; California Sycamore (Platanus racemosa) widespread along the Guadalupe River Park. Juniper (Juniperus) contributes from the Diablo Range foothills. Summer (May-August) sees high Ryegrass (Lolium) and Bermuda Grass (Cynodon dactylon) levels; originating from Coyote Creek and Los Gatos Creek Trail.

Valley topography traps pollen between the Santa Cruz Mountains and Diablo Range. Thermal inversions hold allergens near ground level. Winter rains see elevated Mould (Alternaria, Cladosporium) spore counts; these spores grow from damp organic matter and leaf litter in valley orchards and residential gardens.