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Real-time pollen data for Sunnyvale — updated daily.
Sunnyvale's tree pollen profile reflects its position in the heart of the Santa Clara Valley — a broad alluvial plain flanked by the Santa Cruz Mountains to the west and the Diablo Range to the east, with San Francisco Bay to the north. The valley's Mediterranean climate and decades of ornamental tree planting create an exceptionally diverse urban canopy. Coast live oak, valley oak, and blue oak are native to the surrounding foothills and widely planted throughout Sunnyvale's residential neighborhoods and tech campus landscapes, producing the region's dominant spring allergen from February through April. Bay Area allergists identify oak as the single most important tree allergen in Santa Clara County due to sheer pollen volume during its extended season. Juniper, cedar, and Italian cypress — all in the Cupressaceae family — pollinate from January through May and are among the earliest and most persistent tree allergens in the South Bay. Birch, a non-native ornamental extensively planted across Silicon Valley for its decorative white bark, is highly allergenic and pollinates February through April. Mulberry releases enormous pollen quantities during its brief but intense March–April season. Olive trees, common in commercial and residential landscaping throughout Sunnyvale, produce potent allergenic pollen from April through June. Privet, related to olive and increasingly common as privacy hedging in Sunnyvale's densely built neighborhoods, pollinates as olive season ends and has become a more significant allergen as housing density has increased. Sycamore, ash, walnut, elm, alder, acacia, eucalyptus, and pine add to the diverse tree pollen load. The Heritage Orchard near the Community Center preserves remnants of Sunnyvale's fruit-growing past, and scattered fruit trees throughout older neighborhoods contribute minor spring pollen.
Grass pollen is one of the most significant allergen categories in the South Bay. Bay Area aerobiological surveys consistently show grass pollen season beginning in mid-March and lasting through the end of July — a full four-and-a-half-month window driven by the region's warm, dry spring and summer climate. Perennial ryegrass, Bermuda grass, Timothy grass, wild oats, and brome are prevalent across Sunnyvale's parks, golf courses, athletic fields, corporate campus lawns, and residential yards. Silicon Valley's tech campuses — including facilities operated by Google, Apple, LinkedIn, Amazon, Meta, and others in the Moffett Park area and along major corridors — feature extensive irrigated landscaping that produces substantial grass pollen throughout the growing season. The Santa Clara Valley's foothill grasslands to the west and south support vast stands of non-native annual grasses (wild oats, Italian ryegrass, soft chess) that produce intense spring pollen carried into the valley floor by thermal winds. Sunnyvale's 476 acres of city parks, two golf courses, school athletic fields, and the manicured grounds of its tech office parks create a dense urban grass pollen source. Grass pollen grains are large, highly allergenic, and can travel considerable distances on wind, making avoidance difficult even for residents who maintain low-pollen yards.
Weed pollen levels in the South Bay are generally low to moderate compared to much of the United States — a significant advantage for Sunnyvale allergy sufferers. Bay Area aerobiological surveys have found ragweed to be essentially absent from the region, eliminating what is the dominant fall allergen across most of the country. English plantain, dock, nettle, pigweed, and sheep sorrel are the most common weed allergens, growing along roadsides, creek corridors, vacant lots, and disturbed margins throughout Sunnyvale. Sagebrush (Artemisia) produces fall pollen but in modest quantities compared to Southern California or inland regions. The relatively moderate weed pollen season makes fall considerably more manageable than spring for most Sunnyvale allergy sufferers.
Sunnyvale's northern boundary extends to the San Francisco Bay shoreline, where the Sunnyvale Baylands Park, Don Edwards San Francisco Bay National Wildlife Refuge, and adjacent salt pond restoration areas create extensive wetland habitats. These tidal marshes, managed ponds, and restored wetlands — with their pickleweed, cordgrass, and decaying organic matter — produce significant mold spore loads, particularly during warm humid conditions. Alternaria, Cladosporium, Aspergillus, Ascospores, and Basidiospores are all prevalent in Santa Clara County air surveys, with mold counts remaining elevated even when pollen drops to zero in winter. Marine fog from the Bay regularly blankets northern Sunnyvale, promoting outdoor mold growth. Indoor mold thrives in older homes and in the poorly drained alluvial soils characteristic of the South Bay lowlands where the water table historically sat only 3–5 feet below the surface. Dust mites are a persistent year-round indoor allergen in the Bay Area's moderate humidity. Pet dander affects residents year-round regardless of outdoor conditions.
The Bay Area's mild winter means allergy season starts earlier than most of the country. Juniper, cedar, and cypress begin pollinating as early as January, and by February, alder, acacia, birch, and early oak pollen joins the air. Winter rains promote mold spore growth on decaying vegetation and damp soil — Santa Clara County air surveys show mold counts (particularly Ascospores and Basidiospores) can be moderate to high even when tree pollen is still building. Marine fog from the Bay dampens northern Sunnyvale, fostering outdoor mold on surfaces and in landscaping. Indoor allergens (dust mites, pet dander) are the primary concern as homes are sealed. Severity: Low to Moderate.
The most challenging allergy period in Sunnyvale and across the South Bay. Oak pollen reaches peak concentrations — the single most important tree allergen in Santa Clara County due to the sheer volume of pollen produced by the region's abundant native and planted oaks. Mulberry adds intense but brief pollen bursts (March–April). Birch, elm, ash, sycamore, and walnut contribute to a complex tree pollen mix. Grass pollen begins rising in mid-March as the South Bay's annual grasslands and irrigated urban lawns enter their growth phase. The combination of warming temperatures (highs reaching 65–75°F), decreasing rainfall, and increasing afternoon breezes creates ideal pollen dispersal conditions. Mold counts may remain elevated from winter rains. Severity: High to Very High.
Grass pollen peaks across the South Bay as ryegrass, Bermuda grass, Timothy grass, and wild oats enter their most active pollination. Silicon Valley's extensive irrigated corporate campus lawns and public green spaces produce substantial grass pollen throughout this period. Olive pollen — one of the Bay Area's most potent tree allergens — peaks from April through June, overlapping with the grass season. Privet pollen begins as olive wanes. Late-blooming walnut adds to the tree load. Temperatures climb into the 70s–80s°F range, and the dry season begins in earnest. The combination of high grass pollen, olive pollen, and warming temperatures creates sustained allergy pressure. Severity: High.
Grass pollen declines through July but doesn't fully subside until month's end. Early weed pollen (English plantain, dock, nettle) begins appearing. Dry summer conditions reduce mold temporarily but increase airborne dust particles. This is often the warmest period in the South Bay, with occasional heat waves pushing temperatures above 90°F. Indoor allergens become more significant as residents use air conditioning. South Bay air quality can deteriorate during heat events when atmospheric inversions trap pollutants. Wildfire smoke from elsewhere in California can periodically impact Sunnyvale air quality. Severity: Moderate.
Weed pollen reaches its modest peak with sagebrush, pigweed, and dock. The near-absence of ragweed in the Bay Area makes this period considerably more manageable than in most US cities. Wildfire season risk peaks — fires anywhere in Northern California can send smoke into the South Bay, creating severe air quality episodes that compound allergic conditions. The first fall rains (if they arrive in October) briefly spike mold counts as water activates dormant fungi on the dry landscape. Severity: Low to Moderate (escalating during wildfire smoke events).
Pollen drops to annual lows as the rainy season begins. However, mold spore counts actually increase as fall and winter rains promote fungal growth on decaying organic matter. Santa Clara County air surveys show Ascospores and Basidiospores can reach moderate to high levels in November–December, making this a significant period for mold-allergic individuals despite low pollen. Marine fog returns, dampening northern Sunnyvale. Indoor allergens (dust mites, pet dander, indoor mold) become the primary concern as residents seal homes against cooler weather. Severity: Low (pollen) but Moderate (mold).
If you relocated to Sunnyvale from the Midwest, East Coast, or South, you may notice fall allergies are dramatically milder. Bay Area aerobiological surveys have found ragweed — the dominant fall allergen across most of the United States — to be essentially absent from the region. This makes September and October significantly more manageable for South Bay residents than for allergy sufferers in most other US metros. However, don't assume you're allergy-free: the Bay Area compensates with intense spring tree pollen (especially oak) and a prolonged grass pollen season that can catch transplants off guard.
Unlike many US cities where pollen is the dominant year-round concern, the South Bay has a significant mold spore component that peaks when pollen is lowest. Santa Clara County air surveys show moderate to high mold counts (Ascospores, Basidiospores, Cladosporium, Alternaria) persist through fall and winter, fueled by Bay Area rains and marine fog. If your allergy symptoms worsen in November–January when pollen should be minimal, mold may be your primary trigger. The Sunnyvale Baylands and adjacent salt pond restoration areas along the Bay shoreline are persistent mold sources — northern Sunnyvale neighborhoods near Moffett Park and the 237 corridor experience higher mold exposure.
Sunnyvale's tech campuses feature extensive irrigated lawns and landscaping that produce substantial grass pollen from March through July. If you work at or near the Moffett Park office complexes (Google, Juniper Networks, Lockheed Martin area), the North Mathilda corridor, or other corporate campuses, you're surrounded by manicured grass that pollinates actively during business hours. Keep car windows up during commutes, use recirculated air in your vehicle's HVAC system, and shower after outdoor lunches on campus lawns during peak grass season.
While Sunnyvale itself is not in a wildfire zone, fires anywhere in Northern California — the Santa Cruz Mountains, Diablo Range, Central Valley, or distant Sierra Nevada — can send smoke into the South Bay basin. Recent fire seasons have demonstrated that smoke events can persist for weeks, creating hazardous air quality that severely compounds allergic conditions. Keep N95 masks accessible, monitor AirNow.gov during fire season (typically August–November), and run HEPA air purifiers when smoke is visible or AQI exceeds 100.
Sunnyvale's transformation from the "Garden of the World" — when Santa Clara Valley orchards produced fruit for canning — to Silicon Valley's tech hub replaced low-allergenicity fruit trees with ornamental species chosen for aesthetics rather than allergenic potential. Modern Sunnyvale's urban canopy includes many highly allergenic species: olive, birch, mulberry, privet, and ornamental grasses that produce more allergenic pollen per acre than the apricot, cherry, and plum orchards they replaced.
Sunnyvale's complex allergen environment — intense spring oak and grass pollen, year-round Bay shore mold, olive and privet tree pollen, and periodic wildfire smoke — benefits from specialized evaluation by board-certified allergists who understand the Bay Area's unique patterns. HeyAllergy provides telemedicine appointments from your Sunnyvale home, comprehensive blood allergy testing at a convenient Santa Clara County lab, and personalized treatment plans including HeyPak sublingual immunotherapy drops. Most patients see improvement within 3–6 months, starting at $47/month — no needles, no clinic visits, no waitlist.
March through June is typically the most challenging period, combining peak oak tree pollen with rising grass and olive pollen. Oak pollen is the single most important tree allergen in Santa Clara County, and its season overlaps with the start of a grass pollen season that extends through July. September–October is comparatively mild due to the near-absence of ragweed in the Bay Area.
Oak pollen dominates spring (February–April). Grass pollen from ryegrass, Bermuda, Timothy, and wild oats persists March through July. Olive and privet pollen peak April–June. Juniper/cedar/cypress pollen starts as early as January. Mold spores (Ascospores, Basidiospores, Alternaria, Cladosporium) are significant year-round, peaking in the wet season. Dust mites and pet dander are persistent indoor allergens.
Essentially no. Bay Area aerobiological surveys have found ragweed to be virtually absent from the region. This is a major advantage for Sunnyvale residents compared to most US cities where ragweed is the dominant fall allergen. However, other weed pollens like English plantain, dock, nettle, and sagebrush do produce modest fall pollen.
Yes. Tree pollen begins in January (juniper/cedar) and peaks March–May. Grass pollen dominates March–July. Weed pollen appears August–October. Mold spores are elevated fall through winter, sometimes peaking when pollen is lowest. Indoor allergens persist year-round. There is no truly allergy-free month in the South Bay.
Yes. HeyAllergy provides telemedicine appointments with board-certified allergists licensed in California. Book a virtual consultation, have allergy blood tests ordered to a convenient Santa Clara County lab, and start personalized treatment — all from your Sunnyvale home. No waitlist, fast appointments available.
HeyPak allergy drops use sublingual immunotherapy (SLIT) to gradually desensitize your immune system to your specific triggers — whether oak pollen, grass, olive, mold, dust mites, or other allergens identified in your blood test. You place customized drops under your tongue daily at home. Most patients see improvement within 3–6 months, with 3–5 years recommended for lasting relief.
HeyAllergy accepts Medicare and most major PPO health plans, including United Healthcare, Anthem Blue Cross, Blue Shield, Cigna, Aetna, Humana, Oscar, and Tricare. Contact your insurance provider with Tax ID: 85-0834175 to confirm your specific telemedicine coverage.
The Sunnyvale Baylands, Don Edwards National Wildlife Refuge, and adjacent salt pond restoration areas create extensive tidal marshlands along Sunnyvale's northern boundary. These wetlands produce significant mold spore loads from decaying pickleweed, cordgrass, and organic matter in persistently moist conditions. Residents in northern Sunnyvale near Moffett Park, the 237 corridor, and the Bay shoreline experience higher mold exposure than those in southern residential neighborhoods.
Sunnyvale, a city of approximately 155,000 residents in northwestern Santa Clara County, occupies a pivotal position in the geography that defines Silicon Valley — and that geography equally defines its allergen environment. Situated on the broad alluvial floor of the Santa Clara Valley, Sunnyvale stretches from the San Francisco Bay's tidal marshlands in the north through dense residential and commercial development to the lower slopes approaching the Santa Cruz Mountains in the south. This topographic gradient from sea-level wetlands to valley floor to foothills creates distinct allergen zones within a single city: Bay shore mold in the north, urban tree and grass pollen through the center, and foothill-sourced oak and grassland pollen from the south and west.
Sunnyvale's identity has been shaped by two transformations, both of which fundamentally altered its allergen landscape. The first, beginning in the 1870s, converted wheat farms into fruit orchards — apricot, cherry, plum, and prune trees that made Santa Clara County the "Garden of the World" by 1886. The second, accelerating after World War II, cleared those orchards for the homes, offices, and research facilities that became Silicon Valley. Each transformation brought different plants, different landscaping, and different pollen profiles. Modern Sunnyvale's allergen environment is the product of this layered botanical history.
When Sunnyvale was part of the "Valley of Heart's Delight" — the poetic name for Santa Clara Valley's orchard era — the dominant trees were stone fruits: apricot, cherry, plum, and prune. These trees produced relatively modest allergenic pollen because they relied primarily on insect pollination rather than wind dispersal. The transformation to Silicon Valley replaced these orchards with an entirely different botanical palette: ornamental trees chosen for shade, aesthetics, and fast growth rather than low allergenicity.
Modern Sunnyvale's urban canopy includes many highly allergenic species. Birch, planted extensively for its decorative white bark, is one of the Bay Area's most potent imported allergens. Olive trees, valued for their Mediterranean aesthetic, produce heavy allergenic pollen from April through June. Mulberry, planted as fast-growing shade trees, releases enormous pollen loads during March–April. Privet, increasingly used as privacy hedging as residential density has increased, pollinates as olive season ends. The Heritage Orchard near the Community Center preserves a fragment of the fruit-growing past, but surrounding it on all sides are the high-pollen ornamental trees of the tech-era city.
Sunnyvale's northern boundary extends to the San Francisco Bay, encompassing the Sunnyvale Baylands Park and adjacent wetlands that connect to the Don Edwards San Francisco Bay National Wildlife Refuge — one of the largest urban wildlife refuges in the United States. This area includes extensive salt pond restoration projects, managed seasonal wetlands, tidal marsh, and open water channels. The ecological richness of these habitats comes with an allergenic cost: persistent mold spore production.
The tidal action that twice daily floods and exposes organic-rich marsh sediments creates ideal conditions for allergenic mold species. Decaying pickleweed, cordgrass, and marsh vegetation generate year-round Alternaria, Cladosporium, Aspergillus, and heavy loads of Ascospores and Basidiospores. Santa Clara County air surveys conducted at the San Jose AAAAI pollen station consistently show mold counts remaining moderate even when pollen drops to zero in winter — a pattern driven by the region's wet-season conditions activating fungal growth across the Bay shore wetlands and urban landscapes.
Marine fog from San Francisco Bay regularly blankets northern Sunnyvale, particularly during summer when inland heating draws cool marine air across the Bay. This fog promotes mold growth on outdoor surfaces, in landscaping, and on building exteriors. The poorly drained alluvial soils characteristic of the South Bay lowlands — where the water table historically sat only 3–5 feet below the surface — create persistently damp conditions in crawl spaces and foundations of older homes, fostering indoor mold growth.
Sunnyvale hosts major facilities for Google, Apple, LinkedIn, Amazon, Meta, Walmart Labs, Juniper Networks, Lockheed Martin, and dozens of other technology and aerospace companies. These corporate campuses feature extensive irrigated landscaping — manicured lawns, ornamental tree groves, and designed green spaces intended to create attractive work environments. While aesthetically appealing, these landscapes produce substantial pollen during the growing season.
The Moffett Park area in northwestern Sunnyvale — bounded by the Baylands, Moffett Federal Airfield, and Highway 237 — is undergoing massive transformation from traditional office parks to mixed-use development with significant landscaped areas. This concentration of irrigated green space in close proximity to Bay shore wetlands creates a convergence of grass pollen and mold spore exposure that is particularly challenging for allergic workers and residents in this rapidly developing district.
Sunnyvale's Mediterranean climate — warm, dry summers and cool, wet winters — creates a pollen calendar that differs significantly from most of the United States. The key differences for allergy sufferers include an earlier start to tree pollen season (January for juniper/cedar, February for oak and birch), a prolonged grass pollen season (mid-March through end of July), the near-total absence of ragweed (eliminating what is the dominant fall allergen across most of the country), and a winter mold season that fills the gap when pollen drops. For transplants arriving from other regions, this calendar can be disorienting — expecting relief in fall and finding it, but then experiencing unexpected mold symptoms in winter when other allergens should be dormant.
Sunnyvale's layered allergen environment — intense spring oak and grass pollen, Bay shore mold that peaks when pollen drops, olive and privet pollen extending the tree season into summer, and periodic wildfire smoke from across Northern California — demands specialized understanding that accounts for the Bay Area's unique patterns rather than applying generic national allergy approaches.
HeyAllergy offers Sunnyvale and Santa Clara County residents convenient telemedicine access to board-certified allergists and immunologists who understand the South Bay's specific respiratory challenges. Through a secure video consultation, your allergist can evaluate your complete symptom pattern — including the important distinction between pollen-driven spring symptoms and mold-driven winter symptoms — order comprehensive blood allergy testing at a convenient Santa Clara County lab, and develop a personalized treatment plan. For patients who qualify, HeyPak sublingual immunotherapy drops are customized to your test results and the allergens endemic to the South Bay — including oak, grass, olive, mold, dust mites, and other identified triggers. Delivered directly to your Sunnyvale home and taken daily under the tongue, most patients see improvement within 3–6 months, with 3–5 years recommended for lasting relief. Starting at $47/month — no needles, no clinic visits, no waitlist.
