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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 Fontana — updated daily.
Fontana sits at the base of the San Bernardino Mountains in the western Inland Empire, where the transition from coastal basin to inland desert creates conditions that support a wide range of allergenic trees. Oak trees (coast live oak, valley oak, interior live oak) are among the most significant pollen producers, releasing massive loads from March through May that coat surfaces across the city. Mulberry trees are widely planted as ornamentals throughout Fontana's residential neighborhoods and produce extremely allergenic pollen from March through April — mulberry is considered one of the worst tree allergens in Southern California's inland valleys. Olive trees are cultivated throughout the Inland Empire and produce highly allergenic pollen from April through June. Ash, sycamore, and walnut trees contribute significant spring pollen. Cypress and juniper begin pollinating as early as January and February, often before residents realize allergy season has started. Eucalyptus, planted extensively as windbreaks and ornamentals, produces pollen from late winter through spring. The Inland Empire experiences a more intense blooming season than coastal areas because hotter, drier conditions and Santa Ana winds from the desert stimulate earlier and more prolific pollen production.
Grass pollen is a dominant allergen in the Fontana area, with the warm inland climate extending the grass pollen season significantly longer than coastal Southern California. Bermuda grass is extremely common in lawns, parks, schoolyards, and athletic fields throughout Fontana and is one of the most allergenic grasses in the region. Ryegrass (both annual Italian ryegrass and perennial ryegrass) is prevalent in roadsides, vacant lots, and open spaces. Fescue and orchard grass contribute additional pollen loads. The Inland Empire's hot, dry summers allow grass pollen to remain airborne and concentrated — temperatures regularly exceeding 100°F in Fontana create thermal updrafts that lift pollen high into the air column where it disperses across wide areas. The flat terrain of the Inland Empire basin, combined with surrounding mountains that trap air, means grass pollen concentrations remain elevated for extended periods. Construction of new housing developments and commercial properties continuously disturbs soil and creates new areas where grasses colonize aggressively.
Weed pollen extends Fontana's allergy season deep into fall and early winter. Russian thistle (tumbleweed) is one of the most significant weed allergens in the Inland Empire — it thrives in the dry, disturbed soils common around construction sites, vacant lots, and the desert margins east of the city. Ragweed pollinates from August through October. Sagebrush produces heavy pollen loads from August through November, and its pollen is carried into Fontana from the desert and foothill areas by prevailing winds and Santa Ana events. Amaranth (pigweed), saltbush (atriplex), and wormwood are common throughout the region. Lamb's quarters, dock, and plantain grow in disturbed soils along roadsides and warehouse margins. The explosive warehouse construction across Fontana and surrounding cities creates vast expanses of cleared, disturbed earth where pioneer weed species colonize rapidly — producing heavy pollen loads in areas that were previously agricultural land or open space.
Fontana's inland climate creates significant indoor allergen challenges. Dust mites thrive in bedding, carpeting, and upholstered furniture year-round, though indoor humidity management with air conditioning can help control populations during the dry summer months. Mold becomes particularly problematic during and after the winter rainy season (November through March), especially in older homes with inadequate ventilation. The fine particulate matter from diesel truck exhaust — an estimated 700,000 diesel trucks pass through the Inland Empire daily — infiltrates homes near major transportation corridors including Interstate 15, Interstate 10, and Sierra Avenue. This diesel particulate matter compounds allergic inflammation and worsens asthma. Pet dander is a significant year-round allergen, and cockroach allergen is present in older housing stock throughout the city.
Severity: Moderate to High
Fontana's allergy season begins in January when cypress and juniper trees start releasing pollen during warm spells. By February, ash, alder, and eucalyptus join the pollen count. March brings the beginning of oak, mulberry, and sycamore pollination. Winter in the Inland Empire also means temperature inversions that trap pollutants — including diesel exhaust from the massive warehouse and trucking corridor — near ground level. The San Bernardino Mountains to the north and east block atmospheric dispersion, creating a concentrated layer of smog and particulate matter that compounds the effects of emerging tree pollen. Winter rains can temporarily wash pollen from the air but promote mold growth in damp areas. Santa Ana wind events during winter months can bring desert dust and early weed pollen into the basin.
Severity: High to Severe
Spring through early summer is Fontana's worst allergy period. Oak, olive, mulberry, and walnut tree pollen overlaps with rapidly rising grass pollen — Bermuda, ryegrass, fescue, and orchard grass all peak during this period. The Inland Empire heats dramatically, with temperatures regularly reaching the 90s by May and exceeding 100°F by June. Hot, dry conditions lift pollen high into the air column and concentrate it within the basin's trapped air mass. Ozone levels begin climbing as sunlight reacts with vehicle emissions and diesel exhaust, creating smog that compounds allergic inflammation. This is when Fontana allergy sufferers experience the most severe symptoms — the combination of multiple overlapping pollens, rising ozone, and diesel particulate matter creates a triple burden on the respiratory system.
Severity: Moderate to High
Summer brings extreme heat (consistently exceeding 100°F), the peak of weed pollen season, and increasing wildfire risk. Russian thistle, ragweed, sagebrush, amaranth, and saltbush produce heavy pollen loads from July through September. Ozone levels peak during summer, and the Inland Empire routinely records some of the nation's worst ozone pollution during this period. Wildfire smoke from fires in the San Bernardino National Forest, Angeles National Forest, or Northern California settles into the Inland Empire basin, creating hazardous air quality events that can persist for weeks. The combination of weed pollen, peak ozone, diesel particulate matter, and wildfire smoke makes summer particularly dangerous for anyone with allergic asthma. Santa Ana wind events beginning in September can spike pollen counts overnight by carrying desert allergens into the basin.
Severity: Low to Moderate
Fall provides partial relief as tree and grass pollen subside, but late weed pollen from sagebrush, Russian thistle, and amaranth persists into November. The most significant fall allergy factor is Santa Ana winds — hot, dry winds that blow from the inland deserts through mountain passes (including the Cajon Pass immediately northeast of Fontana) at speeds that can exceed 60 mph. Santa Ana events carry desert dust, fungal spores, and redistributed pollen across the entire Inland Empire basin, causing sudden symptom spikes even when local pollen counts are moderate. These wind events also dramatically increase wildfire risk, with the resulting smoke compounding respiratory distress. By December, outdoor allergens diminish to their lowest levels, but winter temperature inversions begin trapping diesel exhaust and indoor allergens become more prominent as residents close up homes.
Fontana sits at the epicenter of the Inland Empire's massive logistics and warehouse industry. Over 4,000 warehouses operate across the region, with Fontana hosting some of the largest distribution centers in the country. An estimated 700,000 diesel trucks pass through the Inland Empire daily, and many of these trucks travel directly through Fontana on Interstate 15 (the main corridor connecting the Los Angeles ports to the rest of the country) and Interstate 10. Diesel particulate matter is classified as a known carcinogen and produces chronic respiratory inflammation independent of pollen allergies. For allergy sufferers in Fontana, this diesel exposure creates a baseline inflammatory burden that makes pollen reactions more severe — your respiratory system is already inflamed before the first pollen grain arrives. If you live near a major trucking corridor, warehouse cluster, or freight rail line, running HEPA air purifiers in bedrooms and living areas is essential year-round, not just during pollen season.
The Cajon Pass — the major mountain gap between the San Bernardino and San Gabriel Mountains — sits immediately northeast of Fontana and acts as a natural wind tunnel that funnels air between the Inland Empire basin and the high desert. During Santa Ana wind events, hot, dry desert air blasts through the Cajon Pass at speeds that can exceed 60 mph, carrying Mojave Desert dust, fungal spores, and desert weed pollen directly into Fontana and surrounding cities. These events can spike airborne allergen levels overnight and often trigger sudden asthma exacerbations in people who were symptom-free the day before. Monitor weather forecasts for Santa Ana wind warnings (typically September through May), and take preventive antihistamines before symptoms begin. On Santa Ana days, seal windows and doors and run HEPA air purifiers on the highest setting.
Fontana's geography compounds allergen exposure in ways that aren't immediately obvious. The city sits in a basin surrounded by mountains — the San Gabriel Mountains to the northwest, the San Bernardino Mountains to the north and northeast, and lower hills to the south. This basin traps air pollutants, pollen, and diesel exhaust in a stagnant mass that can persist for days or weeks under temperature inversions. San Bernardino and Riverside counties have ranked first and second in the nation for worst ozone pollution. The Inland Empire consistently receives failing grades from the American Lung Association for both ozone and particle pollution. For Fontana residents, this means allergens and respiratory irritants remain concentrated at breathing level far longer than in regions with better atmospheric dispersion — and the health effects are cumulative over time.
Fontana has experienced explosive growth, with new housing developments, commercial construction, and warehouse projects continuously transforming formerly agricultural and open land. Construction activity generates significant dust containing silica, mold spores, and organic particulate matter. More importantly, cleared construction sites are rapidly colonized by allergenic pioneer weeds — Russian thistle, amaranth, ragweed, and various grasses — that produce heavy pollen loads in areas that were previously low-allergen agricultural land or open space. Newly landscaped developments introduce ornamental trees and sod grass (particularly Bermuda grass) that add to the local pollen burden as the urban landscape matures. If you live near active construction or newly completed developments, expect elevated allergen levels and increased dust exposure.
The San Bernardino National Forest begins just miles from Fontana's northern edge, and the Angeles National Forest sits to the northwest. When wildfires burn in these forests — as they do with increasing frequency and intensity — smoke descends directly into the Inland Empire basin where it becomes trapped by the same geography that traps smog and pollen. During major fire events, Fontana can experience hazardous air quality for days or weeks. Wildfire smoke creates a multiplicative inflammatory effect for allergy sufferers — the combination of existing allergic sensitization plus smoke-induced inflammation can trigger severe asthma attacks and prolonged symptom flares. Treating underlying allergies with immunotherapy reduces your overall inflammatory burden and improves resilience during smoke events.
HeyAllergy provides telemedicine appointments with board-certified allergists and immunologists licensed in California. Book a virtual consultation from your Fontana home, have allergy blood tests ordered at a convenient local lab, and receive a personalized treatment plan targeting the specific Inland Empire allergens driving your symptoms — whether oak, mulberry, Bermuda grass, Russian thistle, ragweed, mold, dust mites, or diesel-compounded inflammation. HeyPak sublingual immunotherapy drops ship directly to your door and treat the root cause of allergies by building immune tolerance to your triggers over time. Most patients notice improvement within 3 to 6 months. Starting at $47 per month. HeyAllergy accepts Medicare and most major PPO health plans.
April through June is typically the worst period, with overlapping tree pollen (oak, olive, mulberry, walnut), peak grass pollen (Bermuda, ryegrass, fescue), and rapidly rising ozone levels. The Inland Empire basin traps pollen and pollution, concentrating allergens at breathing level. July through September adds weed pollen, extreme heat, and wildfire smoke risk.
The most common allergens in the Fontana area are oak, mulberry, olive, cypress, Bermuda grass, ryegrass, Russian thistle, ragweed, sagebrush, amaranth, mold spores, and dust mites. Diesel particulate matter from the region's massive warehouse and trucking industry compounds allergic inflammation even when it isn't a true allergen itself.
Fontana sits in a basin surrounded by the San Gabriel and San Bernardino Mountains, which trap pollutants and prevent atmospheric dispersion. Over 700,000 diesel trucks pass through the Inland Empire daily to serve 4,000+ warehouses. San Bernardino County ranks first in the nation for worst ozone pollution. Temperature inversions, Santa Ana winds carrying desert dust, and wildfire smoke all compound the problem.
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 — whether oak, Bermuda grass, Russian thistle, ragweed, mold, or dust mites. 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, 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 specific telemedicine coverage.
Yes, significantly. Santa Ana winds blow hot, dry air from the Mojave Desert through mountain passes like the Cajon Pass directly northeast of Fontana, carrying desert dust, fungal spores, and redistributed pollen at speeds exceeding 60 mph. These events can spike allergen levels overnight and trigger sudden asthma exacerbations. Santa Ana season runs primarily from September through May.
Yes. Diesel particulate matter causes chronic respiratory inflammation independent of pollen allergies. For people with existing allergic sensitization, this baseline inflammation makes pollen reactions more severe. Studies show that communities near warehouse and trucking corridors experience higher rates of asthma, respiratory illness, and emergency department visits. The Inland Empire has been described as a "diesel death zone" by physicians due to these compounding health effects.
Fontana — population approximately 215,000 and one of the largest cities in San Bernardino County — sits at the western edge of the Inland Empire, roughly 50 miles east of downtown Los Angeles at the base of the San Bernardino Mountains. Once known primarily for its steel mill and citrus groves, Fontana has transformed into one of the epicenters of America's logistics industry. The city and surrounding Inland Empire are home to over 4,000 warehouses serving as the primary distribution hub for goods arriving at the ports of Los Angeles and Long Beach. An estimated 700,000 diesel trucks pass through the region daily, generating approximately 50 million pounds of carbon dioxide and depositing massive quantities of diesel particulate matter, nitrogen oxides, and volatile organic compounds into the air Fontana residents breathe. Physicians and community health advocates have described the Inland Empire as a "diesel death zone" due to the high rates of asthma, respiratory illness, and cancer linked to this pollution — and for allergy sufferers, this chronic diesel exposure creates a baseline inflammatory burden that makes seasonal pollen reactions significantly more severe.
Fontana's geography compounds allergen and pollution exposure in ways that make the Inland Empire one of the most challenging environments in the nation for respiratory health. The city sits in a basin surrounded by the San Gabriel Mountains to the northwest, the San Bernardino Mountains to the north and northeast, and lower hills to the south. This mountain-ringed basin functions like a bowl, trapping air pollutants, pollen, diesel exhaust, and wildfire smoke in a stagnant mass that can persist for days or weeks under temperature inversions. San Bernardino and Riverside counties have repeatedly ranked first and second in the nation for worst ozone pollution according to the American Lung Association. The region consistently receives failing grades for both ozone and particle pollution. For allergy sufferers, this means pollen and particulate matter remain concentrated at breathing level far longer and at higher concentrations than in regions with better atmospheric dispersion — and the cumulative health effects are well documented.
The Cajon Pass — the major gap between the San Bernardino and San Gabriel Mountains — sits immediately northeast of Fontana and serves as both a critical transportation corridor (Interstate 15 and BNSF/Union Pacific rail lines) and a natural wind tunnel. During Santa Ana wind events, hot, dry air from the Mojave Desert blasts through the Cajon Pass at speeds that can exceed 60 mph, carrying desert dust, fungal spores (Coccidioides immitis, the cause of Valley Fever, is present in desert soils), and desert weed pollen directly into Fontana and surrounding cities. These wind events can transform air quality overnight — residents who were symptom-free one day may experience severe nasal congestion, asthma exacerbations, and eye irritation the next morning. Santa Ana winds occur primarily from September through May, with peak frequency in October through December, making fall a less reliable period of allergy relief than the weather alone would suggest.
Fontana exemplifies the Inland Empire's warehouse explosion. Over 300 warehouses are located within 1,000 feet of 139 Inland Empire schools. The city's residential neighborhoods are increasingly surrounded by massive distribution centers — Amazon, FedEx, UPS, and hundreds of smaller logistics operations that generate continuous diesel truck traffic on local streets. Research from UC Riverside, NASA, and multiple environmental health organizations has documented that communities near warehouse clusters experience significantly higher rates of asthma, respiratory illness, and emergency department visits. A NASA-funded study found that PM2.5 levels are measurably higher near warehouse clusters, with pollution worsening during the holiday shipping season when truck traffic increases. The diesel particulate matter that saturates the air around these facilities creates chronic low-grade respiratory inflammation that primes the immune system to overreact to pollen and other allergens — essentially lowering the threshold at which seasonal allergens trigger symptoms.
The San Bernardino National Forest begins just miles from Fontana's northern residential neighborhoods, and the Angeles National Forest lies to the northwest. California's increasingly severe wildfire seasons send smoke directly into the Inland Empire basin, where the same geography that traps diesel exhaust and pollen also retains wildfire smoke for days or weeks. For Fontana residents who already carry a significant inflammatory burden from diesel exposure and seasonal allergens, the addition of wildfire smoke creates a multiplicative effect on respiratory health. The immune system, already primed to overreact from chronic pollution exposure and allergic sensitization, can be pushed into severe asthma exacerbations by relatively moderate smoke exposure that might cause only minor irritation in people with healthier baseline respiratory function. This is why the Asthma and Allergy Foundation of America consistently ranks Inland Empire cities among the nation's worst for asthma outcomes.
HeyAllergy connects Fontana residents with board-certified allergists and immunologists licensed in California — providing specialist allergy care without navigating the Inland Empire's notoriously heavy traffic and long specialist wait times. In a region where environmental health challenges compound allergen exposure from every direction — diesel exhaust, trapped basin pollution, Santa Ana desert winds, and increasingly severe wildfire seasons — treating the underlying immune sensitivity is the most effective long-term strategy. A virtual consultation from your Fontana home eliminates the drive and the wait. Allergy blood tests are ordered at a convenient local lab, and a personalized treatment plan targets the specific allergens driving your symptoms. HeyPak sublingual immunotherapy drops ship directly to your door and build your immune system's tolerance to your specific triggers, reducing your overall inflammatory burden in a region where every reduction matters. HeyAllergy accepts Medicare and most major PPO health plans. Starting at $47 per month, with most patients noticing improvement within 3 to 6 months.
