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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 Mateo — updated daily.
Coast live oak produces heavy pollen February-April from Peninsula hillsides. Olive is one of the Bay Area's most potent allergens, peaking April-May. Eucalyptus produces pollen nearly year-round (peaks late winter-spring) and is ubiquitous across the Peninsula. Acacia begins as early as January with intense but short-lived pollen. Redwood pollen peaks February-March. Bay laurel (California bay) releases volatile oils and pollen that trigger respiratory irritation. Monterey cypress and Monterey pine produce winter-spring pollen. Birch, alder, and elm add spring pollen. Ornamental cherry, plum, and other flowering trees are widespread.
Wild oats, ryegrass, and other annual grasses dominate undeveloped hillsides and produce intense spring pollen. Bermuda grass is common in maintained lawns and parks but less dominant than in Southern California. Perennial ryegrass and fescue are widespread in residential and commercial landscaping. Peninsula grasslands produce heavy pollen during the spring growing season triggered by winter rains.
Ragweed is present but less intense than in the eastern US or Texas. Sagebrush, mugwort, and nettle produce moderate fall pollen. Plantain and dock are common. Scotch broom (invasive) produces spring pollen on hillsides. Fennel (invasive) is widespread along roadsides and disturbed areas.
Morning fog and bay-proximity humidity maintain moderate-to-elevated mold levels year-round. Cladosporium is the most common outdoor mold. Alternaria peaks in late summer and fall. Winter rains trigger outdoor mold surges. Coast redwood groves and eucalyptus forest floor decomposition in the western hills produce continuous fungal spores. Bay-adjacent neighborhoods experience the highest mold exposure.
SFO Airport lies immediately north. Aircraft emissions produce ultrafine particulates smaller than PM2.5 that penetrate deep into lungs. Northern San Mateo neighborhoods under flight paths experience the highest exposure. Functions as allergen amplifier.
US-101, Highway 92, and El Camino Real diesel particulates and PM2.5. Caltrain diesel commuter rail. Functions as allergen amplifier concentrated along transportation corridors.
Dust mites are moderate-to-elevated due to bay-proximity and fog-driven humidity. Pet dander is significant. Indoor mold risk exists in older homes, particularly those near the Bay shoreline or in fog-prone areas with poor ventilation.
Severity: Low to Moderate. Winter rains trigger mold surges on forest floor and in bay-adjacent areas. Eucalyptus continues year-round pollen. Acacia begins producing as early as January. Indoor dust mites and pet dander peak with closed-window heating. Fog-driven humidity persists. Monterey cypress produces winter pollen.
Severity: Moderate to High. Redwood pollen peaks February-March. Acacia in full bloom. Oak begins active pollination on Peninsula hillsides. Birch and alder produce early pollen. Eucalyptus pollen increases. Peninsula grasslands begin greening with winter rain-triggered growth. Morning fog concentrates pollen at breathing height.
Severity: Severe. San Mateo's worst allergy period. Olive peaks April-May (one of the Bay Area's most potent allergens). Oak peaks. Eucalyptus continues. Bay laurel, Monterey pine, and ornamental trees overlap. Wild oat and ryegrass pollen surges on Peninsula hillsides. Multiple allergen types airborne simultaneously. Fog-to-sun morning transition creates dual exposure pattern.
Severity: High. Annual grasses peak on hillsides before drying out. Bermuda and ryegrass continue on irrigated lawns. Summer fog pattern strengthens, trapping morning allergens. Tree pollen tapers. Alternaria mold begins increasing. Bay-proximity humidity elevates dust mites.
Severity: Moderate to High. Late grass pollen on irrigated surfaces. Ragweed, mugwort, and nettle produce fall pollen. Alternaria peaks. Dried hillside grasses generate dust and particulate matter. Eucalyptus continues. Bay fog persists through mornings.
Severity: Moderate. Late ragweed and mugwort taper. First fall rains (typically October-November) trigger brief mold surges and begin next season's grass greening cycle. Scotch broom and fennel produce late pollen. Leaf decomposition under eucalyptus and oak groves generates Cladosporium and Aspergillus.
San Mateo sits on the bayside (eastern) half of the San Francisco Peninsula, shielded from direct Pacific fog by the Santa Cruz Mountains to the west. This creates a distinctive microclimate: morning fog and cool air may push through gaps like the Crystal Springs corridor, but afternoons are typically sunny and warmer than San Francisco or coastal Peninsula communities. This fog-then-sun pattern concentrates pollen at breathing height during cool, humid mornings, then releases it as the air warms and dries by midday. If your symptoms are worse in the morning, fog-trapped pollen is likely the trigger.
The Bay Area's tree pollen season is intense and extended. Acacia begins as early as January. Olive peaks April-May and is one of the most potent allergens in the region. Coast live oak produces heavy pollen February-April from hillside woodland. Eucalyptus — originally planted as windbreaks and now naturalized across the Peninsula — produces year-round pollen but peaks in late winter and spring. Bay laurel (California bay), redwood, and Monterey cypress add distinctive Peninsula pollen not found in Southern California. If you've relocated from Southern California or out of state, these Northern California species create a genuinely different allergen profile.
San Francisco International Airport (SFO) is immediately north of San Mateo. Aircraft taking off and landing release ultrafine particulates that can affect nearby communities. While the impact diminishes with distance from the airport, northern San Mateo neighborhoods and areas under flight paths experience measurably higher ultrafine particulate exposure. These particles amplify biological allergen responses and worsen asthma.
US-101 runs through San Mateo's eastern portion, and Highway 92 connects the bayside to the coast (Half Moon Bay). Combined with El Camino Real (State Route 82), these corridors carry heavy commuter traffic. Diesel particulate and PM2.5 from this traffic amplify biological allergen responses. Time outdoor exercise for early morning before traffic builds or for parks away from major corridors.
The Santa Cruz Mountains west of San Mateo support coast redwood groves, Monterey pine, Douglas fir, and extensive eucalyptus stands. These species produce pollen that drifts downslope into bayside communities on afternoon westerly breezes. Eucalyptus pollen is particularly significant — the trees are ubiquitous across the Peninsula and produce pollen nearly year-round. Redwood pollen peaks February-March. These are distinctive Northern California allergens not found in our Southern California or other state pages.
San Mateo's eastern neighborhoods border San Francisco Bay tidal marshlands and fill areas. This bay proximity maintains elevated humidity compared to inland Peninsula communities, creating conditions favorable for mold and dust mites. Homes near Seal Point Park, Ryder Park, and the Bay Trail along the shoreline experience the highest moisture-driven mold exposure. Run dehumidifiers in bay-adjacent homes, especially during foggy periods and winter rain season.
February through May brings peak tree pollen with oak, olive, eucalyptus, acacia, and redwood producing overlapping waves. Grass pollen peaks April through August on Peninsula hillsides. July through November adds weed pollen. Mold is moderate-to-elevated year-round due to fog and bay proximity. Morning fog traps allergens at breathing height throughout the year.
San Mateo sits on the bayside of the San Francisco Peninsula, shielded from direct Pacific fog by the Santa Cruz Mountains but receiving fog through gaps like the Crystal Springs corridor. This creates morning fog that concentrates pollen at breathing height, followed by sunny afternoons. Bay proximity maintains humidity that elevates mold and dust mites. Western hills produce distinctive Northern California tree pollen (redwood, eucalyptus, bay laurel) that drifts downslope.
Yes — significantly. Northern California Peninsula allergens include coast redwood, eucalyptus, bay laurel, Monterey cypress, acacia, and birch — species rarely or never found in Southern California. Grass species differ (wild oats vs Bermuda-dominant). The fog-driven microclimate creates different mold patterns. Patients relocating from SoCal often develop new sensitizations within 1-3 years.
SFO Airport sits immediately north of San Mateo. Aircraft ultrafine particulates can affect nearby neighborhoods, particularly those under flight paths. These particles don't cause allergies but amplify biological allergen responses and worsen asthma.
Yes. HeyAllergy provides telemedicine appointments with board-certified allergists licensed in California. No waitlist. Available throughout the San Francisco Peninsula including San Mateo, Burlingame, Foster City, Redwood City, San Carlos, Belmont, and surrounding communities.
HeyPak® sublingual immunotherapy drops are customized based on allergy blood test results. For San Mateo residents, this targets local oak, olive, eucalyptus, redwood, acacia, ryegrass, ragweed, mold, and dust mite allergens specific to the Northern California Peninsula. Daily drops retrain your immune system with improvement in 3–6 months. Starting at $47/month.
HeyAllergy accepts Medicare and most major PPO health plans, including United Healthcare, Anthem Blue Cross, Blue Shield, Cigna, Aetna, Humana, Oscar, and Tricare. Tax ID: 85-0834175.
San Mateo is a city of approximately 106,000 residents in San Mateo County, California, situated on the San Francisco Peninsula approximately 20 miles south of San Francisco and 30 miles north of San Jose. The city sits on the bayside (eastern) half of the Peninsula between San Francisco Bay to the east and the Santa Cruz Mountains to the west. As the county seat of San Mateo County, the city anchors a corridor of Peninsula communities that form the geographic bridge between San Francisco and Silicon Valley. San Mateo's location creates a distinctive allergen environment shaped by Bay Area microclimates, Peninsula ecology, and the interplay between marine fog, bay moisture, and sheltered inland warmth.
The San Francisco Peninsula is a narrow land mass bounded by the Pacific Ocean to the west and San Francisco Bay to the east, with the Santa Cruz Mountains running along its spine. San Mateo occupies the bayside slope, shielded from direct Pacific fog by the mountain ridge but receiving fog that penetrates through gaps — particularly the Crystal Springs corridor to the southwest. This creates the characteristic Peninsula microclimate: cool, foggy mornings that burn off to warm, sunny afternoons. San Mateo is typically warmer and sunnier than San Francisco or coastal communities like Pacifica and Half Moon Bay, but cooler than inland South Bay cities like San Jose. Annual precipitation averages approximately 20 inches concentrated November through March.
The Santa Cruz Mountains west of San Mateo support distinctive Northern California ecosystems: coast redwood groves, mixed evergreen forest (Douglas fir, Monterey pine, tanoak), and extensive eucalyptus plantations originally established as windbreaks in the late 19th century. These species produce allergens fundamentally different from Southern California: redwood pollen (February-March), eucalyptus (nearly year-round), bay laurel (California bay) producing volatile oils that can trigger respiratory irritation, and Monterey cypress. The bayside supports coast live oak woodland, introduced ornamental landscapes, and remnant tidal marsh along the shoreline. This ecological diversity creates a layered allergen environment unique to the Peninsula.
San Mateo's eastern boundary follows the San Francisco Bay shoreline, including areas of tidal marsh, bay fill, and waterfront parks (Seal Point Park, Ryder Park, Bay Trail). This bay proximity maintains elevated humidity in eastern neighborhoods and supports marsh and shoreline vegetation that produces pollen and mold. The Bay's moderating influence prevents temperature extremes but also maintains moisture levels that favor dust mite and mold proliferation. Sea level rise and king tide flooding are emerging concerns for low-lying bayside areas.
San Mateo sits at the center of the Peninsula tech corridor between San Francisco and Silicon Valley. US-101 runs through the city's eastern portion, Highway 92 connects to Half Moon Bay across the mountains, and El Camino Real (SR-82) is a major local arterial. Caltrain commuter rail serves the city with stations connecting to SF and San Jose. SFO Airport is immediately to the north, placing portions of San Mateo under flight paths. This transportation infrastructure generates diesel particulate, PM2.5, and aircraft ultrafine particulate exposure that amplifies biological allergen responses.
San Mateo's Peninsula microclimate with morning fog trapping allergens, distinctive Northern California tree species (redwood, eucalyptus, bay laurel, Monterey cypress), bay-proximity moisture driving mold and dust mite proliferation, SFO airport ultrafine particulates, US-101 corridor diesel pollution, and Crystal Springs gap fog penetration create an allergy environment unique on the San Francisco Peninsula. HeyAllergy connects San Mateo residents with board-certified allergists through telemedicine. Patients receive allergy blood testing, personalized treatment, and HeyPak® sublingual immunotherapy drops custom-formulated for Northern California Peninsula allergens. Treatment starts at $47/month. No needles, no clinic visits, no waitlist.
