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Real-time pollen data for Pasadena — updated daily.
Pasadena's extraordinary urban tree canopy — the city's signature aesthetic of tree-lined streets, historic neighborhoods, and landscaped estates — makes tree pollen one of the most intense allergen categories in the San Gabriel Valley. Coast live oak and valley oak are the dominant native tree allergens, producing heavy pollen from March through May. California sycamore (the iconic tree of Pasadena's Arroyo Seco) produces allergenic pollen in spring. Olive trees, widely planted as ornamentals throughout Pasadena's older neighborhoods, produce highly allergenic pollen from April through June. Ash, mulberry (one of the most intensely allergenic trees in Southern California), walnut, and eucalyptus are common street and landscape trees. Acacia blooms early, sometimes beginning in January. The San Gabriel Mountains rising immediately north of Pasadena support native oak woodland, California bay laurel, and foothill vegetation that contributes natural pollen carried downslope on morning drainage winds. The Arroyo Seco watershed — the natural canyon that runs through western Pasadena, home to the Rose Bowl — harbors dense native sycamore, oak, and riparian vegetation. Pasadena's mature residential canopy, developed over more than a century of landscaping in the city's Craftsman bungalow and estate neighborhoods, ensures pollen sources surround residents from every direction.
Grass pollen is a prolonged allergen in Pasadena, driven by Southern California's warm climate and the city's extensive landscaped areas. Bermuda grass is the dominant warm-season lawn grass, producing heavy pollen from April through September. Ryegrass (used for winter overseeding), bluegrass, Timothy grass, and fescue contribute. The Rose Bowl's maintained turf, Brookside Golf Club, the expansive lawns of Caltech's campus, and residential lawns throughout Pasadena's neighborhoods all produce grass pollen. The mild climate means Bermuda grass may produce measurable pollen even in winter on warm days. The San Gabriel Valley's inland position creates warmer summer temperatures than coastal communities, extending and intensifying the grass pollen season.
Ragweed, Russian thistle (tumbleweed), and mugwort are the primary fall weed allergens in Pasadena. Sagebrush (Artemisia californica) is native to the coastal sage scrub that covers the lower slopes of the San Gabriel Mountains and the Arroyo Seco hillsides — this native vegetation produces fall pollen carried into Pasadena neighborhoods on downslope winds. Pigweed (amaranth), lamb's quarters, and nettle contribute. Santa Ana winds — hot, dry desert winds from the northeast — pass directly over or through the San Gabriel Mountains and can spike pollen counts dramatically, carrying weed pollen and dust from the Inland Empire and high desert across the San Gabriel Valley. Southern California's warm autumn extends weed pollen into November.
Pasadena's position at the northern edge of the San Gabriel Valley places it against the San Gabriel Mountains, which act as a barrier that traps air pollution in the LA Basin. The same geography that creates Pasadena's dramatic mountain backdrop also traps ozone, particulate matter, and other pollutants against the mountain front. On hot summer days and during temperature inversions, the San Gabriel Valley can experience some of the worst air quality in the LA Basin as smog accumulates against the mountains. Research shows ozone and particulate matter damage airway linings and amplify the body's immune response to biological allergens. For Pasadena residents, the mountain-trapped air quality is effectively an allergen multiplier that makes pollen and mold more potent than the same concentrations would be in cleaner air.
Mold is a year-round allergen in Pasadena. Winter rains (November–March) activate outdoor mold on soil, leaf litter, and organic material, with Alternaria and Cladosporium as dominant species. The Arroyo Seco's riparian habitat and Pasadena's heavily treed neighborhoods generate substantial leaf litter that decomposes and supports mold growth. Indoor mold grows year-round in bathrooms, kitchens, and older homes with poor ventilation — particularly relevant in Pasadena's significant stock of historic Craftsman-era homes (many built 1900–1930s) that may have older construction without modern moisture barriers. Dust mites thrive year-round in the mild climate. Pet dander is a constant trigger.
Winter rains wash pollen from the air temporarily but activate outdoor mold growth. Acacia and eucalyptus begin producing pollen as early as January. Indoor allergens (dust mites, pet dander, indoor mold) are active year-round. The San Gabriel Valley's mild winters mean there is no true pollen-free period. Mountain drainage winds on clear mornings can bring foothill plant pollen downslope into residential areas. Severity: Low to Moderate.
This is typically Pasadena's most intense allergy period. Oak pollen peaks across the city's dense canopy and the Arroyo Seco's native oak woodland. Sycamore, olive, ash, mulberry, and walnut add to the load. Grass pollen begins rising as Bermuda grass enters active growth. Spring winds can carry mountain-slope pollen into the valley. The overlap of peak tree pollen with rising grass pollen creates a compound burden. Severity: High to Very High.
Grass pollen peaks as Bermuda grass, ryegrass, and bluegrass reach maximum production. Late tree pollen (olive, mulberry) extends into May. Temperatures climb and ozone levels begin rising in the San Gabriel Valley. Smog accumulates against the mountain front on hot, still days. Severity: High.
Ragweed begins in late summer and peaks in September. Sagebrush pollen from the San Gabriel Mountain foothills and Arroyo Seco contributes. Russian thistle and mugwort add fall weed pollen. Ozone levels peak during summer heat. Santa Ana wind events — most common September through November — can spike pollen and degrade air quality with hot desert air flowing over the mountains. September is often one of Pasadena's worst months as weed pollen combines with Santa Ana risk and peak smog. Severity: Moderate to High (Very High during Santa Ana events).
Ragweed and Russian thistle can persist into November. Santa Ana winds remain a risk. Fall rains begin promoting mold growth. Sagebrush pollen from the foothills continues. The transition toward winter brings cooling temperatures and gradually improving air quality. Severity: Moderate, declining.
Pasadena's iconic San Gabriel Mountain backdrop acts as a wall that traps air pollution, pollen, and other airborne particles in the San Gabriel Valley. On hot, still summer days, smog and ozone concentrate against the mountain front exactly where Pasadena sits. This trapped air quality amplifies your allergic response to pollen. Check both pollen AND AQI forecasts daily — when both are elevated, the compound effect can be severe. HEPA air purifiers are essential in San Gabriel Valley homes.
The Arroyo Seco — the natural canyon running through western Pasadena that houses the Rose Bowl, Brookside Park, and connects to the San Gabriel Mountains — is lined with native sycamore, oak, and sage scrub that produce allergenic pollen. If you live near the Arroyo, exercise along its trails, or attend events at the Rose Bowl, your allergen exposure may be significantly higher than Pasadena's general forecast suggests.
Olive trees are widely planted as ornamentals throughout Pasadena's older neighborhoods, particularly in the historic districts. Olive pollen is one of the most allergenic tree pollens in Southern California, peaking April through June. If you have olive trees on or near your property, you may experience significantly higher tree pollen exposure during spring.
Santa Ana winds pass directly over the San Gabriel Mountains into the valley, carrying weed pollen, dust, and particulate from the high desert and Inland Empire. These events can transform a moderate allergy day into a severe one within hours. Monitor Santa Ana forecasts (typically September–November) and premedicate on expected wind days.
Pasadena's treasured Craftsman bungalows and historic estates (many built 1900–1930s) are architecturally significant but may lack modern moisture barriers, ventilation standards, and waterproofing. If you live in an older Pasadena home and experience symptoms that worsen indoors, particularly after rain, hidden mold in walls, foundations, or crawl spaces may be contributing.
Pasadena's combination of dense tree canopy, mountain-trapped air quality, Arroyo Seco native vegetation, and year-round allergen cycling creates one of the most complex allergy environments in the LA metro area. HeyAllergy's board-certified allergists provide telemedicine appointments to Pasadena residents — comprehensive blood testing at a convenient local lab and personalized HeyPak allergy drops delivered to your home. Most patients see improvement within 3–6 months, starting at $47/month — no needles, no clinic visits, no waitlist.
March–April (peak oak and tree pollen) and September (peak ragweed plus Santa Ana wind risk and peak ozone) are typically the worst. Pasadena's Mediterranean climate means there is no truly pollen-free month. Tree pollen runs February through May, grass pollen April through September, weed pollen July through November, and mold is active year-round.
Oak and sycamore dominate spring tree pollen. Olive trees are highly allergenic April–June. Bermuda grass and ryegrass peak in summer. Ragweed, sagebrush, and Russian thistle peak in fall. Air pollution trapped against the San Gabriel Mountains amplifies all allergic responses. Mold, dust mites, and pet dander are year-round indoor triggers.
The mountains act as a barrier that traps air pollution and pollen in the San Gabriel Valley. On hot, still days, ozone and particulate matter accumulate against the mountain front. This trapped air quality amplifies your allergic response to biological allergens, making the same pollen count cause worse symptoms than in areas with better air circulation.
Yes. The Arroyo Seco canyon is lined with native sycamore, oak, and coastal sage scrub that produce allergenic pollen. The riparian habitat supports elevated mold. Homes near the Arroyo and people who exercise along its trails or visit the Rose Bowl area experience higher allergen exposure than neighborhoods further from the canyon.
Yes. HeyAllergy provides telemedicine appointments with board-certified allergists licensed in California. Book a virtual consultation, have allergy blood tests ordered to a convenient Pasadena-area lab, and start personalized treatment — all from 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, sycamore, olive, Bermuda grass, ragweed, 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, Health Net, Anthem Blue Cross, Blue Shield, Cigna, Aetna, Humana, Oscar, and Tricare. Contact your insurance provider with Tax ID: 85-0834175 to confirm your telemedicine coverage.
Santa Ana winds blow from the northeast, passing directly over or through the San Gabriel Mountains into the valley. They carry weed pollen, dust, and particulate matter from the high desert and Inland Empire, spiking pollen counts and degrading air quality within hours. These events are most common September through November.
Pasadena, California — a city of approximately 140,000 residents in the western San Gabriel Valley — is renowned for the Tournament of Roses, the Rose Bowl, Caltech, NASA's Jet Propulsion Laboratory, and its stunning Craftsman-era architecture. But Pasadena's defining geographic feature — its position at the base of the San Gabriel Mountains — also creates one of the most distinctive allergy environments in the Los Angeles metropolitan area.
The San Gabriel Mountains rise dramatically to over 10,000 feet immediately north of Pasadena, forming a wall that defines the northern edge of the LA Basin. This mountain barrier has two critical effects on respiratory health: it traps air pollution and pollen in the valley below, and its foothill slopes support native vegetation — oak woodland, coastal sage scrub, chaparral — that produces allergenic pollen carried downslope into residential neighborhoods. Combined with Pasadena's remarkable urban tree canopy, mild Mediterranean climate, and year-round allergen exposure, this geography creates an allergy landscape more complex than most LA Basin communities face.
The San Gabriel Mountains are one of the steepest and most dramatic urban-adjacent mountain ranges in the United States. For Pasadena, they create a striking visual backdrop — and a persistent air quality challenge. Air pollution generated across the LA Basin drifts north and east on prevailing sea breezes, then stalls against the mountain wall. On hot summer days and during temperature inversions, ozone and particulate matter concentrate in the San Gabriel Valley's trapped air. Pasadena, sitting at the mountain front, is one of the first communities to experience this concentration.
The health implication is direct: particulate matter and ozone damage airway linings, increase mucosal permeability, and amplify the body's inflammatory response to biological allergens. For Pasadena residents, the same oak pollen count that might cause mild sneezing in a community with clean, well-circulated air can trigger moderate to severe symptoms in the valley's trapped atmosphere. Air quality is not separate from allergy management in Pasadena — it is a central component.
The Arroyo Seco ("dry stream" in Spanish) is the natural canyon that runs through western Pasadena from the San Gabriel Mountains to the LA River. This historic waterway — home to the Rose Bowl, Brookside Park, and the Arroyo's famous trail system — is one of Pasadena's most beloved natural features. It also creates a concentrated allergen corridor through the heart of the city.
The Arroyo's canyon walls and floodplain support native California sycamore (one of the most iconic trees of Southern California riparian areas), coast live oak, California bay laurel, and extensive coastal sage scrub dominated by allergenic California sagebrush. The riparian habitat maintains higher moisture levels than surrounding neighborhoods, supporting mold growth. During morning hours, cool air draining down the canyon from the mountains carries foothill pollen into the neighborhoods below. For residents who live along the Arroyo or who exercise, walk dogs, or attend events at the Rose Bowl, allergen exposure from the canyon's vegetation is a regular and often underrecognized factor.
Pasadena's urban tree canopy is one of its most celebrated characteristics. The city's Craftsman-era neighborhoods, established primarily between 1900 and 1930, were planted with mature oaks, sycamores, ash, olive, and eucalyptus that have grown into a dense canopy over more than a century. These trees are part of Pasadena's identity — and part of its allergy challenge. During peak tree pollen season (March–May), the mature canopy means pollen sources surround residents on every street. Olive trees, planted extensively as ornamentals, produce some of the most allergenic pollen in Southern California.
Pasadena's combination of mountain-trapped air quality, Arroyo Seco native vegetation, century-old tree canopy, and year-round Mediterranean pollen cycling creates an allergy environment that demands comprehensive management.
HeyAllergy's board-certified allergists understand the specific allergen challenges of the San Gabriel Valley. Through a secure telemedicine consultation, your allergist can evaluate your complete symptom pattern — including the interaction between biological allergens and valley air quality — order comprehensive blood allergy testing at a convenient Pasadena-area lab, and develop a personalized treatment plan. HeyPak sublingual immunotherapy drops are customized to your specific triggers and the allergens endemic to the San Gabriel Valley, including oak, sycamore, olive, Bermuda grass, ragweed, sagebrush, dust mites, and mold. Delivered to your home, taken daily under the tongue, most patients see improvement within 3–6 months. Starting at $47/month — no needles, no clinic visits, no waitlist.
