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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 Bernardino — updated daily.
San Bernardino sits at the base of the San Bernardino Mountains at roughly 1,000 feet elevation — higher than most Southern California valley floors — where the transition from semi-arid basin to mountain chaparral creates a unique mix of urban and foothill tree allergens. Oak is the dominant tree allergen, with coast live oak and valley oak producing heavy pollen from February through May. Juniper and cypress release pollen as early as January, often the first allergenic trees of the year. Ash, walnut, and mulberry contribute significant spring pollen — mulberry in particular produces massive pollen loads and is one of the most allergenic trees in Southern California. Olive trees, widely planted as ornamentals throughout the Inland Empire, release highly allergenic pollen from April through June. Sycamore lines many older streets and contributes spring pollen. The San Bernardino National Forest — 680,000 acres rising directly above the city — harbors extensive stands of pine, incense cedar, and Jeffrey pine at higher elevations. While conifer pollen is relatively less allergenic, the sheer volume produced by these mountain forests creates visible yellow pollen clouds that descend into the valley during spring wind events. Eucalyptus pollinates nearly year-round.
Grass pollen is a major allergen in San Bernardino from spring through late summer. Bermuda grass is the most significant grass allergen in the Inland Empire, thriving in the hot, dry climate and present in nearly every landscaped area, park, athletic field, and residential yard. Ryegrass contributes from April through June. Bent grass, orchard grass, and fescue — common in irrigated lawns and golf courses — add to the grass pollen burden. Unlike coastal Southern California where ocean breezes moderate grass growth, San Bernardino's inland heat accelerates grass pollination and creates higher pollen concentrations. Summer temperatures routinely exceed 100°F, which dries grass seed heads and releases pollen that remains airborne in the hot, rising air.
Fall weed season brings some of San Bernardino's most distinctive allergens. Ragweed pollinates from August through October, though it is less dominant here than in eastern states. Russian thistle (tumbleweed) is a significant allergen across the Inland Empire — this non-native invasive thrives in disturbed soil, vacant lots, and along extensive freeway corridors. Saltbush is native to the region and produces highly allergenic pollen from late summer through fall. Sagebrush releases pollen from August through November, with prevalence increasing on the foothill slopes where coastal sage scrub dominates. Amaranth and wormwood contribute additional fall weed pollen. The Santa Ana winds — hot, dry wind events that funnel through the Cajon Pass directly into San Bernardino — can spike weed pollen concentrations dramatically by stripping pollen from plants across the entire basin and carrying desert allergens from the Mojave.
Indoor allergens are a persistent year-round concern. Dust mites thrive despite the arid climate because irrigated landscaping and residential water use maintain indoor humidity levels sufficient for mite populations, and evaporative coolers — still used in many older Inland Empire homes — add moisture directly to indoor air. Mold grows in air conditioning systems, under sinks, and where irrigation creates moisture against building foundations. Cockroach allergen is a significant asthma trigger in the densely populated urban core. Pet dander from cats and dogs is a perennial indoor allergen. San Bernardino's air quality challenges — the worst ozone pollution in the nation — compound indoor allergen exposure because residents are advised to stay indoors on high-pollution days, increasing contact with dust mites, mold, and pet dander in closed environments.
Severity: Low to Moderate
The allergy year begins with juniper and cypress pollen in January, often overlapping with the tail end of winter rain season. Oak catkins begin forming in February. Winter temperature inversions trap cold air in the San Bernardino Valley basin — bounded by mountains on the north, east, and south — creating stagnant air that concentrates both allergens and pollution near the ground. These inversions can persist for days, particularly during calm, clear weather between storm systems. PM2.5 from fireplace smoke and diesel trucks accumulates during inversions, irritating airways already sensitized by early tree pollen.
Severity: High to Severe
Spring is San Bernardino's most intense tree pollen period. Oak reaches peak levels from March through April. Ash, mulberry, walnut, and olive overlap to create sustained high pollen counts through May. Mulberry is particularly problematic — a single tree can produce billions of pollen grains. Grass pollen begins rising in April. This multi-allergen overlap creates the first severe allergy period. Warmer spring days increase ozone formation, and the combination of peak pollen and rising ozone creates a double burden — inflamed airways from pollen become more vulnerable to ozone damage, and ozone-irritated airways become more reactive to pollen. Santa Ana winds can still occur through May.
Severity: Moderate to High
Summer shifts the dominant allergen from trees to grasses, with Bermuda grass and ryegrass at peak levels through July. Temperatures routinely exceed 100°F and can reach 115°F during heat waves, driving maximum ozone production — San Bernardino County experiences approximately 150 to 175 unhealthy ozone days per year, the worst in the nation. Late July through August brings the start of weed pollen. Wildfire season begins, and smoke from fires in the San Bernardino National Forest can blanket the valley for days. The combination of grass pollen, ozone, and potential wildfire smoke makes summer the most challenging period for respiratory health.
Severity: Moderate to High
Fall brings peak ragweed, Russian thistle, saltbush, sagebrush, and amaranth weed pollen. Santa Ana winds funnel through the Cajon Pass into San Bernardino at speeds approaching 60 mph, stripping pollen from plants, carrying desert dust and Mojave allergens, and preventing normal pollen settling. They also dramatically increase wildfire danger — October through November is historically the peak wildfire period. The convergence of weed pollen, Santa Ana winds, potential wildfire smoke, and residual ozone creates a multi-threat environment unique to San Bernardino.
Severity: Low
December offers San Bernardino's best relief window. Winter rains wash pollen from the air. Most plants are dormant. However, indoor allergens intensify as residents close windows and run heating systems that circulate dust mites and indoor mold. This is the optimal window to begin allergy treatment before the spring pollen surge.
San Bernardino sits directly at the mouth of the Cajon Pass — the gap between the San Gabriel and San Bernardino Mountains where I-15 connects the Mojave Desert to the Inland Empire. This pass functions as a natural wind tunnel, channeling Santa Ana winds directly into the city at speeds approaching 60 mph. These hot, dry winds carry desert dust, Mojave allergens, pollen stripped from foothill chaparral and sage scrub, and particulate matter traveling hundreds of miles. Santa Ana events most commonly occur October through May. During these episodes, pollen counts can spike three to five times above normal within hours. Monitor wind forecasts and plan indoor days during Santa Ana warnings. HEPA air purifiers become essential equipment during these events.
San Bernardino County has been ranked the worst county in the entire United States for ozone pollution by the American Lung Association — experiencing approximately 150 to 175 unhealthy smog days per year. Ozone inflames and damages the delicate lining of airways, making them hyperreactive to pollen and other allergens. If you find that your allergies are significantly worse in San Bernardino than when you visit coastal areas, the ozone burden on top of allergen exposure is likely the explanation. Standard antihistamines treat the allergic response but do nothing to address chronic airway inflammation from ozone. A board-certified allergist can develop a comprehensive treatment plan addressing both allergen sensitivity and the inflammatory burden of living in the nation's smoggiest city.
San Bernardino is the logistics hub of the American West, with over 4,000 warehouses across the Inland Empire generating more than 200 million diesel truck trips per year. The BNSF Railway intermodal yard operates in the city, and I-10, I-215, and SR-210 funnel thousands of diesel trucks daily through residential neighborhoods. Diesel particulate matter is a documented asthma trigger that makes allergic responses more severe. Surveys found over 70 percent of San Bernardino residents reported respiratory issues in their family. If you live near a warehouse corridor or major freeway, air purifiers with activated carbon filters can help reduce indoor diesel particulate exposure.
The San Bernardino National Forest rises directly above the city — 680,000 acres of chaparral, sage scrub, and conifer forest that regularly burns during fire season. During wildfire events, smoke fills the valley basin and can persist for days due to the same mountain-ringed geography that traps smog. Wildfire smoke contains PM2.5 that penetrates deep into lungs, inflammatory compounds, and partially combusted plant proteins that can trigger allergic responses. Create an indoor clean air room with sealed windows and a HEPA purifier before fire season. Stock N95 masks. Monitor AirNow.gov during fire events.
Many older San Bernardino homes use evaporative coolers that pull outdoor air through wet pads — bringing pollen, dust, and particulate matter directly indoors while adding moisture that promotes dust mite growth and mold. During high-pollen days, Santa Ana events, or wildfire smoke, evaporative coolers actively worsen indoor air quality. Supplement with standalone HEPA purifiers in bedrooms. Change cooler pads monthly during pollen season. Consider upgrading to refrigerated AC — in a city with the nation's worst ozone, the ability to seal and filter indoor air is a medical necessity.
HeyAllergy offers telemedicine appointments with board-certified allergists licensed in California — providing expert allergy care without sitting in traffic on I-215 or breathing diesel exhaust in a clinic parking lot. Book a virtual consultation, have allergy blood tests ordered at a local lab, and receive a personalized treatment plan. HeyPak sublingual immunotherapy drops ship directly to your door and treat the root cause of allergies by building tolerance to your specific triggers. In a city where the nation's worst ozone, Cajon Pass winds, wildfire smoke, and warehouse diesel exhaust compound every allergic reaction, treating the underlying sensitivity is the most effective path to lasting relief. Most patients notice improvement within 3 to 6 months. Starting at $47 per month.
March through May is the worst period for pollen, driven by overlapping oak, mulberry, ash, walnut, and olive tree pollen plus rising grass pollen. June through August adds the nation's worst ozone pollution and potential wildfire smoke. September through November brings weed pollen amplified by Santa Ana winds funneling through the Cajon Pass.
The most common allergens are oak, mulberry, olive, Bermuda grass, ryegrass, ragweed, Russian thistle, saltbush, sagebrush, dust mites, mold, cockroach allergen, and pet dander. San Bernardino's Inland Empire location means higher pollen concentrations than coastal areas because no ocean breeze moderates them, and the mountain-ringed valley basin traps allergens.
San Bernardino County has the worst ozone pollution in the nation — approximately 150 to 175 unhealthy smog days per year. Ozone inflames airways and makes them hyperreactive to pollen. Add diesel particulate from the warehouse industry, Santa Ana winds through the Cajon Pass carrying desert allergens, and periodic wildfire smoke — a multi-layered respiratory burden that coastal cities do not experience.
Yes. HeyAllergy provides telemedicine appointments with board-certified allergists and immunologists licensed in California. Book a virtual consultation from anywhere in the state, have allergy blood tests ordered at a local lab, and start a personalized treatment plan without visiting a clinic. No referral needed and no waitlist.
HeyPak sublingual immunotherapy uses customized liquid drops placed under your tongue daily containing precise doses of the specific allergens triggering your symptoms. Over time, your immune system builds tolerance, reducing allergic reactions and medication dependence. Most patients notice improvement within 3 to 6 months.
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.
Essentially yes. Tree pollen runs January through May, grass pollen April through August, weed pollen August through November, and indoor allergens are continuous. December offers the best relief window but even then indoor allergens and occasional Santa Ana events prevent a complete break. The nation's worst ozone adds a year-round inflammatory burden.
Wildfire smoke from the San Bernardino National Forest contains fine particulate matter that penetrates deep into lungs, inflammatory compounds, and partially combusted plant proteins that can trigger allergic responses. The mountain-ringed valley basin traps smoke for days or weeks. People with existing allergies or asthma are at highest risk during fire events.
San Bernardino — population approximately 222,000 — occupies a unique geographic position at the base of the San Bernardino Mountains in the western Inland Empire. The city sits at roughly 1,000 feet elevation on the floor of the San Bernardino Valley, a basin bounded by the eastern San Gabriel Mountains to the northwest, the San Bernardino Mountains to the north and east, the San Jacinto Mountains to the southeast, and the Temescal and Santa Ana Mountains to the south. This mountain-ringed geography creates a natural bowl that traps air pollutants and allergens, preventing their dispersal. The same topography that gives San Bernardino its dramatic mountain backdrop creates the atmospheric conditions that have made it the smoggiest place in the nation. For allergy sufferers, pollen released into the valley has nowhere to go — it accumulates in the basin air, concentrations build throughout the day, and only strong wind events or rain can clear it.
The Cajon Pass is a narrow gap between the San Gabriel and San Bernardino Mountain ranges at the northwest corner of the valley, carrying Interstate 15 and the BNSF Railway between the Mojave Desert and the Inland Empire. This pass functions as a natural wind tunnel, channeling air masses between the desert and the coast. During Santa Ana wind events — most common October through May — hot, dry air from the high desert funnels through the Cajon Pass and blasts directly into San Bernardino at speeds approaching 60 mph. These winds carry Mojave Desert dust, pollen from desert plants including sagebrush and saltbush, and fine particulate matter documented traveling hundreds of miles. For residents, a Santa Ana event transforms the allergen profile overnight — suddenly exposed to desert allergens that don't normally grow locally, combined with locally produced pollen stripped from every plant surface and kept airborne far longer than on calm days. The same pass also channels BNSF freight trains and I-15 truck traffic, adding diesel particulate to the wind-driven allergen load.
The American Lung Association has consistently ranked San Bernardino County as the worst county in the entire United States for ozone pollution. The county experiences approximately 150 to 175 unhealthy ozone days per year — roughly five to six months when ground-level ozone reaches levels harmful to human health. Ozone is a powerful lung irritant that reacts with the delicate lining of airways, causing inflammation comparable to sunburn inside the lungs. For allergy sufferers, this chronic airway inflammation amplifies every allergic response. Airways already irritated by ozone become hyperreactive to pollen, dust mites, and other allergens, producing stronger symptoms from the same allergen exposure that would cause milder reactions in cleaner air. The ozone forms when nitrogen oxides from vehicle exhaust and volatile organic compounds react with intense Southern California sunlight. San Bernardino's geography concentrates these precursor pollutants in the valley basin, and abundant sunshine drives maximum ozone production during summer months. Per IQAir's 2024 World Air Quality Report, San Bernardino ranked among the top five most polluted cities in North America for PM2.5.
San Bernardino is ground zero for America's logistics industry. The Inland Empire houses over 4,000 warehouses generating more than 200 million diesel truck trips per year and producing over 300,000 pounds of diesel particulate matter annually. The city hosts the BNSF Railway intermodal freight yard and is bisected by I-10, I-215, and SR-210 — major freight corridors funneling thousands of diesel trucks through residential neighborhoods daily. The California Air Resources Board designated the San Bernardino and Muscoy community as a priority area under Assembly Bill 617, acknowledging that 6 rail yards and warehouse clusters impact 68 schools, 38 daycare facilities, and 11 hospitals within the community boundary. Surveys by community organizations found that over 70 percent of residents reported respiratory issues in their family or neighborhood. Some census tracts have asthma rates approaching 20 percent. Diesel particulate matter triggers asthma attacks and sensitizes allergic airways — the warehouse industry doesn't just add respiratory disease, it amplifies the allergic burden from pollen and other allergens.
The San Bernardino National Forest — 680,000 acres of chaparral, coastal sage scrub, oak woodland, and conifer forest — rises directly above the city. The foothill vegetation is primarily chaparral and sage scrub at lower elevations, transitioning to pine and mixed conifer forest above 5,000 feet. California's fire season regularly produces major burns in these mountains — the 2003 Old Fire burned over 91,000 acres and directly threatened San Bernardino neighborhoods. During wildfire events, smoke fills the valley basin — the same mountain-ringed geography that traps ozone and diesel exhaust also traps wildfire smoke, sometimes for days or weeks. Wildfire smoke contains fine particulate matter that bypasses the body's defenses and lodges deep in lung tissue, inflammatory organic compounds, and partially combusted plant proteins from burning chaparral that can trigger immunological responses.
What makes San Bernardino's allergy environment truly distinctive is the synergy between natural allergens and anthropogenic pollution. Research has demonstrated that air pollutants like ozone and diesel particulate matter do not simply coexist with pollen — they interact. Ozone can break down pollen grains into smaller fragments that penetrate deeper into airways. Diesel exhaust particles can enhance the immune system's allergic response to pollen. Nitrogen dioxide increases airway permeability, allowing allergens to cross into tissue more readily. In San Bernardino, where all three pollutants are present at among the highest concentrations in the nation within a mountain-ringed basin, the effective allergen burden is far greater than pollen counts alone suggest. This helps explain why standard antihistamines often fail to provide adequate relief — they address only the histamine response while doing nothing about the inflammatory priming from pollution that amplifies it.
HeyAllergy's telemedicine platform connects San Bernardino residents to board-certified allergists and immunologists licensed in California — providing expert care without adding another drive through diesel truck traffic on congested freeways. A virtual consultation eliminates waiting rooms and scheduling delays. Allergy blood tests are ordered at a convenient local lab, and a personalized treatment plan is developed based on your specific triggers. HeyPak sublingual immunotherapy drops ship directly to your door and treat the root cause of allergies by building tolerance to the specific allergens driving your symptoms — whether oak, mulberry, Bermuda grass, ragweed, Russian thistle, dust mites, mold, or pet dander. In a city where the nation's worst ozone, Cajon Pass wind events, wildfire smoke, and warehouse diesel exhaust compound every allergic reaction, treating the underlying allergic sensitivity is the most effective path to lasting relief. HeyAllergy accepts Medicare and most major PPO health plans. Starting at $47 per month, with most patients noticing improvement within 3 to 6 months.
