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*Disclaimer: HeyAllergy® provides all clinical services furnished to patients in California, Florida, Texas, Illinois, Nevada, Pennsylvania. In New York, clinical services are furnished by Hey Allergy Medicine.
Real-time pollen data for San Jose — updated daily. Powered by board-certified allergists.
Tree pollen dominates San Jose's spring allergy season. Oak trees are the most significant trigger in the South Bay, with coast live oak and valley oak producing heavy pollen loads from March through May. Birch, maple, walnut, mulberry, elm, and olive trees also contribute substantially. Juniper and cedar trees can begin releasing pollen as early as January during mild winters. Olive trees, planted extensively throughout San Jose neighborhoods and commercial landscapes, produce highly allergenic pollen from March through May.
San Jose's position at the southern end of the San Francisco Bay, surrounded by the Diablo Range to the east and the Santa Cruz Mountains to the west, creates a valley effect where tree pollen from surrounding hillsides concentrates in the urban basin. Morning breezes from the Bay push pollen inland, while afternoon onshore winds can recirculate it.
Bermuda grass, ryegrass, Timothy grass, bent grass, and bluegrass are the primary grass allergens in San Jose. Grass pollen peaks from May through July and typically declines by late August. San Jose's extensive parks — including Alum Rock Park, Guadalupe River Park, and the many neighborhood parks throughout the valley — along with residential lawns and the grassy foothills of the Diablo Range, are major grass pollen sources.
The dry summer climate of the Santa Clara Valley means grass pollen remains airborne longer than in humid cities. Warm, windy afternoons create peak grass pollen conditions, while mornings and evenings tend to have lower concentrations.
Ragweed, sagebrush, mugwort, pigweed, lamb's quarters, and Russian thistle are the key fall allergens in San Jose. Ragweed pollen peaks in September and October, with sagebrush contributing significantly in areas bordering the foothills and open spaces. The undeveloped hillsides and wildland-urban interface areas throughout eastern and southern San Jose harbor dense weed growth that produces concentrated pollen loads.
Mold is a significant year-round allergen in San Jose. The AAAAI-certified San Jose pollen station (Station No. 1) documents mold spore counts throughout the year, with Ascospores and Basidiospores as the predominant types. Fall mold counts can reach moderate to heavy levels — data from November 2025 showed over 8,400 mold spores per cubic meter. Mold thrives in the damp conditions that follow the Bay Area's first fall and winter rains, growing on decomposing vegetation, outdoor surfaces, and in homes with moisture issues.
Dust mites thrive in San Jose's moderate temperatures and are a significant year-round allergen, particularly from October through March when homes are more frequently closed up. San Jose's older housing stock in downtown, Willow Glen, and Japantown neighborhoods can harbor mold and dust mite concentrations. Pet dander from cats and dogs adds to the constant indoor allergen load. Silicon Valley's culture of working from home has increased indoor allergen exposure for many residents who spend extended hours in their home offices.
San Jose's mild winters mean the allergy season can start as early as late January. Juniper and cedar trees begin releasing pollen during warm spells, and alder trees are early contributors. Bay Area winter rains create ideal conditions for mold growth, with Ascospores and Basidiospores reaching moderate levels on decomposing vegetation and outdoor surfaces. Indoor allergens — dust mites, pet dander, and indoor mold — are at their peak as residents keep windows closed.
Top allergens: Juniper, alder, mold spores, dust mites
Severity: Low to moderate (outdoor), moderate (indoor/mold)
Tip: January rain in San Jose doesn't mean allergy relief — it means mold surges. If your symptoms worsen after rainstorms, mold is likely a trigger. Run HEPA air purifiers and address any moisture issues in your home during the rainy season.
This is San Jose's most intense allergy period. Oak pollen peaks from March through May, with coast live oak and valley oak as the primary triggers. Birch, maple, walnut, olive, mulberry, and elm trees add to the pollen load. The Santa Clara Valley's geography concentrates pollen from surrounding hillsides in the urban basin. April and May are typically the worst months, with tree pollen overlapping with early grass pollen by late April.
Top allergens: Oak (dominant), birch, olive, maple, walnut, mulberry, early grass
Severity: High to very high
Tip: San Jose Station No. 1 — an AAAAI-certified pollen counting station — provides accurate local pollen data for Santa Clara County. Check their readings during peak spring season to plan outdoor time. Start allergy medications by early March before oak pollen ramps up.
Grass pollen peaks in June and early July, with Bermuda grass and ryegrass as the primary triggers. San Jose's dry summer climate keeps grass pollen airborne longer than in humid cities. By late July and August, grass pollen begins declining, but the brown, dry hillsides of the Diablo Range release dust and residual pollen on windy days. Summer is San Jose's most comfortable allergy season for tree-sensitive individuals, though grass-allergic residents still struggle through July.
Top allergens: Bermuda grass, ryegrass, Timothy grass, airborne dust
Severity: Moderate (declining through summer)
Tip: San Jose's dry summers mean pollen doesn't get washed away by rain. Windy afternoons in the valley create peak grass pollen conditions. Time outdoor exercise for mornings or evenings when pollen counts are lower.
Ragweed and sagebrush dominate fall, peaking in September and October. The first fall rains — typically arriving in October or November — trigger dramatic mold spore surges as dormant mold colonies reactivate on moisture-starved surfaces. The AAAAI San Jose station has recorded fall mold counts exceeding 8,000 spores per cubic meter. This combination of weed pollen and resurgent mold makes October one of San Jose's most challenging allergy months.
Top allergens: Ragweed, sagebrush, mugwort, mold spores (Ascospores, Basidiospores)
Severity: Moderate to high
Tip: The first fall rain in San Jose is not allergy relief — it's a mold trigger. Expect symptoms to spike 24–48 hours after the first significant rain as mold explodes on previously dry surfaces. Premedicate and run air purifiers.
December brings the lowest outdoor pollen counts but continued mold activity during the rainy season. Indoor allergens become dominant as homes are sealed for winter. Dust mites and pet dander concentrate in living spaces. Natural Christmas trees can introduce mold spores into homes.
Top allergens: Indoor mold, dust mites, pet dander
Severity: Low (outdoor), moderate (indoor)
Tip: Use the winter low-pollen window to start HeyPak® sublingual immunotherapy and build tolerance before spring arrives.
San Jose sits in a geographic basin — the Santa Clara Valley — bordered by the Diablo Range to the east and the Santa Cruz Mountains to the west. This valley geography channels and concentrates pollen from surrounding hillsides into the urban area. Morning bay breezes push pollen inland, while afternoon onshore winds recirculate it. On days with light wind and temperature inversions, pollen can stagnate over the valley floor at high concentrations. Residents living near the foothills in East San Jose, Evergreen, and Almaden often experience higher pollen exposure than those closer to downtown.
San Jose has an AAAAI-certified pollen counting station (Station No. 1) operated by a local allergist. This station provides specific daily counts for trees, grasses, weeds, and mold spores for the Santa Clara County area. The data is the most accurate local source available and far more relevant than national forecast models. Check readings during peak spring (March–May) and fall (September–October) seasons before planning outdoor activities.
San Jose's Mediterranean climate means months of dry summer weather followed by the first significant rain in October or November. When that rain arrives, mold colonies that have been dormant on dry surfaces reactivate explosively. Fall mold counts at the San Jose station have exceeded 8,000 spores per cubic meter — categorized as moderate to heavy. If your allergy symptoms suddenly spike after the first fall rain, mold is almost certainly the trigger. Run HEPA air purifiers, keep windows closed for 48 hours after rain, and address any outdoor mold growth on decks, patios, and building surfaces.
San Jose's tech-driven culture means many residents spend extended hours indoors — in home offices, open-plan tech campuses, and climate-controlled buildings. This increases exposure to indoor allergens: dust mites, pet dander (many Silicon Valley workers have pets at home during remote work), and indoor mold. If your symptoms are worst in the morning, at night, or during indoor work hours, indoor allergens may be a bigger factor than outdoor pollen. Invest in HEPA air purifiers for your home office, encase bedding in dust-mite-proof covers, and ensure adequate ventilation in spaces where you spend the most time.
Pollen in the Santa Clara Valley follows predictable daily patterns: tree pollen tends to peak from mid-morning through early afternoon, while grass pollen peaks in the afternoon and early evening. Morning joggers on the Guadalupe River Trail or Los Gatos Creek Trail may encounter peak tree pollen, while evening runners face grass pollen. The lowest pollen window in San Jose is typically early morning before 7 AM and after sunset. Plan outdoor exercise accordingly during peak spring and early summer seasons.
San Jose's extended allergy season — from January through November with year-round mold — means cycling through OTC antihistamines for months on end. HeyAllergy's board-certified allergists can identify your specific triggers through blood testing and create a personalized HeyPak® sublingual immunotherapy plan formulated for the Bay Area's allergen profile. Most patients notice improvement within 3–6 months. Book a telemedicine consultation from anywhere in the South Bay — no clinic visit needed, no waitlist.
April and May are typically the worst for tree pollen, with oak as the dominant allergen. September is severe due to ragweed and sagebrush. October can be surprisingly bad when the first fall rain triggers a mold spore explosion after months of dry weather. Overall, San Jose's allergy season runs from late January through November.
Outdoor pollen season runs approximately from late January through November — about 10 months. December and early January are the lowest outdoor pollen period, but mold spores remain elevated during the rainy season, and indoor allergens (dust mites, pet dander) persist year-round. There's no truly allergy-free month in San Jose.
San Jose sits in a geographic basin between the Diablo Range and Santa Cruz Mountains. This valley geography channels and concentrates pollen from surrounding hillsides into the urban area. Temperature inversions and light-wind days can trap pollen over the valley floor, creating sustained high-concentration periods that open-terrain cities don't experience.
Yes. HeyAllergy provides telemedicine appointments with board-certified allergists licensed in California. You can book a virtual consultation, have allergy blood tests ordered at a local lab, receive a diagnosis, and start treatment — all without visiting a clinic. No waitlist.
HeyAllergy's HeyPak® sublingual immunotherapy drops are customized based on your blood allergy test results and formulated with allergens specific to the San Jose region — including oak, birch, olive, Bermuda grass, ragweed, dust mites, and mold. You place drops under your tongue daily at home. Over 3–6 months, your immune system builds tolerance, reducing symptoms and medication dependence.
HeyAllergy accepts Medicare and most major PPO health plans, including United Healthcare, Health Net, Anthem Blue Cross, Blue Shield, Cigna, Aetna, Humana, Oscar, and Tricare. Telemedicine benefits vary by plan — contact your insurance provider with HeyAllergy's Tax ID (85-0834175) to confirm your specific coverage.
Mold is measurably present year-round in San Jose, but spikes dramatically after the first fall and winter rains (typically October–November). After months of dry summer weather, the first rain reactivates dormant mold colonies on outdoor surfaces, producing counts that can exceed 8,000 spores per cubic meter. Fall and winter rainy season are San Jose's worst months for mold exposure.
HeyAllergy has no waitlist. You can book an online appointment at a time that works for you and see a board-certified allergist via secure video consultation — typically within days, not weeks. Available for residents throughout the South Bay including San Jose, Santa Clara, Sunnyvale, Cupertino, Mountain View, Milpitas, and Campbell.
San Jose occupies the heart of the Santa Clara Valley — a broad, flat basin bounded by the Diablo Range to the east and the Santa Cruz Mountains to the west. This geography creates a natural pollen concentration effect that distinguishes San Jose from coastal Bay Area cities like San Francisco and Oakland. Pollen from oak-covered hillsides, grassland foothills, and wildland areas surrounding the valley drifts into the urban basin on morning breezes from the Bay, while afternoon onshore winds recirculate it. On days with light wind or temperature inversions, pollen can stagnate over the valley floor at elevated concentrations for extended periods.
This valley effect, combined with San Jose's Mediterranean climate — warm, dry summers and mild, wet winters — creates an allergy season that stretches approximately 10 months, from late January through November. The 1.03 million residents of San Jose face one of California's most complex allergen environments, where geographic amplification meets an extended growing season.
San Jose is the economic heart of Silicon Valley, and the tech industry's culture has allergy implications that are often overlooked. The widespread adoption of remote and hybrid work means many South Bay residents spend extended hours in home offices — environments that accumulate dust mites, pet dander (especially with pets present during work hours), and indoor mold. Open-plan tech offices and corporate campuses with recirculated air can also concentrate indoor allergens.
For tech workers who transitioned to remote work, the shift from climate-controlled office buildings with commercial HVAC filtration to residential spaces with residential-grade systems has often increased indoor allergen exposure. If your allergy symptoms worsened when you started working from home, your home office environment may be a contributing factor. Investing in a quality HEPA air purifier for your workspace can make a meaningful difference.
San Jose's Mediterranean climate creates a unique mold dynamic. After months of dry summer weather (typically June through September with virtually no rainfall), the first significant rain of fall arrives in October or November. This rain reactivates dormant mold colonies that have been sitting on dry surfaces all summer. The result is an explosive mold spore release that the AAAAI-certified San Jose pollen station has documented at over 8,000 spores per cubic meter — with Ascospores and Basidiospores as the predominant types.
For mold-sensitive residents, the first fall rain is not a welcome relief from dry conditions but a trigger event. Symptoms can spike dramatically within 24–48 hours of the first rain and remain elevated throughout the winter rainy season. Understanding this pattern is critical for San Jose allergy management, because many residents assume rain should help their allergies and are confused when symptoms worsen.
San Jose's park system and surrounding open spaces are treasured community assets — from Alum Rock Park in the eastern foothills to the Guadalupe River Park winding through downtown to the Santa Teresa and Almaden Quicksilver county parks in the south. The city's eastern and southern neighborhoods border the Diablo Range foothills and Santa Cruz Mountains, creating a wildland-urban interface where native vegetation meets residential development.
These areas are concentrated allergen sources: oak woodlands produce heavy spring pollen, native grasses release pollen through summer, and sagebrush, mugwort, and other native weeds produce fall pollen. Residents in foothill-adjacent communities like Evergreen, Silver Creek, Almaden Valley, and the eastern portions of the Berryessa district often experience higher allergen exposure than those living closer to downtown or the Bay shoreline.
The Santa Clara Valley periodically experiences poor air quality from traffic emissions, industrial activity, and, increasingly, wildfire smoke during California fire season (typically August through November). Air pollution interacts with pollen to make it more allergenic — research has shown that pollen grains exposed to pollutants and particulate matter can trigger stronger immune responses. On days when air quality is poor and pollen is elevated simultaneously, allergy sufferers may experience more severe symptoms than either factor alone would produce.
Wildfire smoke from fires in the Santa Cruz Mountains, Diablo Range, or Northern California creates particularly challenging conditions for residents with allergies and asthma. The combination of fine particulate matter (PM2.5) and airborne allergens during smoke events can cause acute respiratory symptoms even in people who don't typically suffer from allergies.
Getting to specialist appointments in San Jose means navigating Highway 101, I-280, I-880, or Highway 87 — some of the most congested corridors in the Bay Area. Silicon Valley's traffic and the demands of tech industry schedules make regular in-person allergy visits impractical for many residents. Traditional allergy clinics in the South Bay often have extended wait times for new patients.
HeyAllergy eliminates these barriers. Residents from San Jose to Santa Clara to Sunnyvale to Cupertino to Mountain View to Milpitas can see a board-certified allergist from home via secure video consultation — fitting easily into a lunch break or after-hours schedule. Blood allergy tests can be ordered to a convenient local lab, and a personalized treatment plan including HeyPak® sublingual immunotherapy drops formulated for the Bay Area's allergen profile can begin without a single in-person visit. No needles, no Highway 101 traffic, no waitlist.
If your allergy symptoms stretch from spring through fall, if the first fall rain makes your symptoms worse instead of better, if you live near the foothills and have chronic congestion, if working from home has worsened your allergy symptoms, if OTC medications aren't providing adequate relief through San Jose's extended allergy season, if you have both allergies and asthma, or if wildfire smoke events exacerbate your respiratory symptoms, it's time to see a board-certified allergist.
HeyAllergy accepts Medicare and most major PPO health plans, making expert allergy care accessible for residents throughout the South Bay and greater Silicon Valley.
