San Jose, CA Pollen Levels Today

San Jose's location in the southern Santa Clara Valley, sheltered by the Santa Cruz Mountains and Diablo Range, creates a mild Mediterranean climate with wet winters and long, dry summers—conditions that support a nearly year-round allergy season.

Tree pollen typically kicks off the calendar from February through May, with oak, olive, walnut, mulberry, ash, elm, and sycamore among the most prolific local offenders; coast live oak in particular produces heavy pollen loads across the valley's hillsides and neighborhoods.

As trees taper, grass pollen takes over from April through July, driven by Bermuda, ryegrass, Kentucky bluegrass, orchard grass, and wild oats that flourish in the valley's dry grasslands and irrigated lawns.

Weed season follows in late summer and fall, dominated by Russian thistle (tumbleweed), pigweed, lamb's quarters, sagebrush, and plantain; true ragweed is less intense here than in the Midwest but still contributes.

Spring overlap between tree and grass pollen often intensifies symptoms from April into May.

Beyond pollen, dry summer winds stir dust and particulates, wildfire smoke is a growing seasonal factor, and indoor mold can spike during the damp winter months.

Overall, San Jose's allergy profile is defined by an extended, overlapping pollen calendar layered with dust and smoke.