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Real-time pollen data for Brownsville — updated daily.
Brownsville's subtropical location at the southern tip of Texas means tree pollen season starts earlier and lasts longer than almost anywhere else in the state. Mesquite (Prosopis glandulosa) is the dominant tree across the Rio Grande Valley's Tamaulipan thornscrub landscape, pollinating from March through May with peak intensity in April. Huisache (Acacia farnesiana), with its distinctive yellow puffball flowers, is one of the Valley's most prolific pollen producers, blooming as early as January and continuing through March. Live oak (Quercus virginiana) grows in scattered mottes throughout Cameron County and produces heavy pollen loads from February through April. Ash trees pollinate from February through April, with Mexican ash native to the Rio Grande corridor. Retama, Texas ebony, anacua, sugar hackberry, and cedar elm are additional native species that contribute to the subtropical tree pollen mix. The mild winters mean some trees may pollinate sporadically even in December and January, giving Brownsville one of the longest tree pollen seasons in the United States.
Grass pollen is Brownsville's most persistent biological allergen, with an extraordinarily long season driven by the subtropical climate. Bermuda grass is the dominant species, thriving on irrigated lawns, parks, Fort Brown Memorial Golf Course, and agricultural edges throughout Cameron County. Bermuda grass can pollinate from March through November in Brownsville's warm climate — nearly nine months of continuous exposure. Johnson grass, a tall aggressive species found along roadsides, irrigation canals, and disturbed agricultural land, adds heavy pollen loads from April through October. Buffalograss and various native grama grasses from the surrounding Tamaulipan grasslands contribute additional pollen. The irrigated agricultural landscape surrounding Brownsville — including sugarcane, sorghum, and cotton fields — creates vast open areas where grass species colonize margins and ditches, producing pollen that Gulf breezes carry into the city.
Ragweed is a major fall allergen in Brownsville, pollinating from August through November with peak concentrations in September and October. A single ragweed plant can produce over one billion pollen grains per season, and the flat, open Rio Grande Valley terrain allows ragweed pollen to travel vast distances on prevailing winds. Pigweed (amaranth) thrives in Brownsville's disturbed urban soils and agricultural margins, pollinating through much of the warm season. Lamb's quarters, marsh elder, and various chenopods add to the weed pollen burden. Sagebrush from the drier inland brush country west of Brownsville contributes fall pollen carried eastward by occasional wind shifts. The mild subtropical climate means weed pollen season extends later than in most Texas cities, with some species continuing to pollinate into December before the brief cool season suppresses growth.
Brownsville's high humidity is a mold paradise. Average relative humidity ranges from 60–85% year-round, with morning humidity regularly exceeding 90% due to Gulf of Mexico moisture. Alternaria, Cladosporium, Aspergillus, and Penicillium mold species thrive outdoors on decaying vegetation, in soil, and on building surfaces. The city's network of resacas — historic oxbow lakes of the Rio Grande that wind through neighborhoods — creates permanent moisture reservoirs where mold colonies flourish year-round. Hurricane and tropical storm flooding can produce explosive mold growth in affected homes and standing water areas. Dust mites thrive in Brownsville's humid indoor environments without needing air conditioning condensation to create favorable conditions — the ambient humidity is already ideal for their reproduction. Pet dander and cockroach allergens are significant year-round indoor triggers throughout the Rio Grande Valley.
While most of Texas is still in winter dormancy, Brownsville's subtropical climate triggers early pollination. Huisache trees burst into yellow bloom as early as mid-January, filling the air with pollen. Mountain cedar pollen from the Hill Country can drift southward on north winds during cold fronts. Ash and live oak begin pollinating by February. Mold spore counts remain moderate to high year-round due to persistent humidity. Gulf moisture keeps relative humidity above 70% most mornings. Severity: Moderate to High.
Brownsville's most intense allergy period begins. Mesquite — the dominant tree of the Tamaulipan thornscrub — peaks in April, with pollen from millions of mesquite trees across Cameron County. Live oak pollen peaks in March, coating vehicles and outdoor surfaces with yellow-green dust. Bermuda and Johnson grass pollen surge as the subtropical warmth accelerates growth. The overlap of peak tree pollen with rising grass pollen creates sustained high allergen exposure. Humidity-driven mold remains elevated. Severity: Very High.
Tree pollen gradually declines but grass pollen reaches peak intensity. Bermuda grass produces maximum pollen loads in warm, humid conditions — exactly what Brownsville provides. Johnson grass lines roadsides and irrigation canal banks throughout the Valley. Temperatures climb into the 90s with high humidity, creating oppressive conditions that keep residents indoors with air conditioning, increasing indoor allergen exposure. Early tropical storm activity can bring flooding that triggers mold surges. Severity: High.
Extreme heat (frequently exceeding 100°F) suppresses some grass pollen production, but Bermuda grass continues pollinating. Ragweed begins its season in August, joining persistent grass pollen for an overlap period. Hurricane season peaks, and tropical moisture increases humidity to extreme levels — morning readings frequently exceed 90%. Mold spore counts reach their annual peak. Indoor environments become critical as residents seal homes for air conditioning, concentrating dust mites, pet dander, and cockroach allergens. Severity: High (mold and indoor allergens), Moderate (outdoor pollen).
Ragweed pollen reaches its annual peak across the Rio Grande Valley. The flat, open terrain allows ragweed pollen to travel for miles on prevailing Gulf breezes and occasional north winds from cold front passages. Pigweed, lamb's quarters, and marsh elder add to the weed pollen burden. Bermuda grass continues pollinating through October. Hurricane and tropical storm remnants can bring flooding that produces explosive mold growth. Severity: Very High.
Brownsville's mild winters extend allergy season later than almost anywhere in Texas. Ragweed continues into November. Some grass species persist until December's brief cool period. Mold remains elevated due to persistent humidity. The first strong cold fronts of the season can bring mountain cedar pollen from Central Texas. December offers the closest thing to allergy relief, but indoor allergens — dust mites, mold, cockroach, pet dander — thrive year-round in Brownsville's humid homes. Severity: Moderate (November), Low to Moderate (December).
Brownsville's average humidity of 60–85% is ideal for mold and dust mites — year-round, without seasonal variation. Unlike drier Texas cities where indoor humidity is the main concern, Brownsville requires aggressive dehumidification. Run air conditioning consistently (it dehumidifies as it cools), use standalone dehumidifiers in bedrooms and living areas, and target indoor humidity below 50%. Pay special attention to rooms near resacas, where ambient moisture from these oxbow lakes can elevate indoor humidity levels in adjacent homes.
Brownsville's unique network of resacas — historic oxbow lakes of the Rio Grande that wind through residential neighborhoods — creates permanent moisture environments where mold thrives. If you live near a resaca, your mold exposure is likely higher than average. Keep windows closed, maintain air filtration, and watch for mold growth on exterior walls and in HVAC systems. After heavy rains or tropical storms that raise resaca water levels, check for water intrusion and address any dampness immediately to prevent mold colonization.
Bermuda grass pollinates from March through November in Brownsville — one of the longest grass pollen seasons in the country. If you're sensitive to grass, this is not a problem you can wait out. Consider proactive allergy testing to confirm grass sensitivity and explore long-term immunotherapy rather than relying on antihistamines for three-quarters of the year. Time lawn mowing for late afternoon when pollen has settled, and shower immediately after outdoor yard work.
The Rio Grande Valley's signature tree allergens — mesquite and huisache — are different from the oak-cedar cycle that Central Texas is known for. Huisache blooms remarkably early (January–March), while mesquite peaks in April. These native thornscrub species produce copious wind-dispersed pollen that no amount of urban development can eliminate because they grow throughout the surrounding brush country for hundreds of miles in every direction. Track local pollen counts rather than relying on statewide Texas allergy calendars, which are typically based on Austin or Houston patterns.
Brownsville's location at the southern tip of Texas places it directly in the path of Gulf of Mexico hurricanes and tropical storms (June–November). When these storms bring flooding — which is a regular occurrence in the flat, low-lying Rio Grande Valley — the resulting standing water and saturated building materials create explosive mold growth within 24–48 hours. Have a post-storm mold prevention plan: extract standing water immediately, run dehumidifiers and fans, remove saturated materials promptly, and wear N95 masks during cleanup. Mold exposure during post-storm cleanup is one of the most intense allergen events Brownsville residents face.
Unlike cities with distinct allergy seasons that provide natural relief periods, Brownsville's subtropical climate means allergen exposure is essentially continuous. If you've been managing symptoms with over-the-counter medications for years without resolution, your immune system may benefit from a targeted approach. Comprehensive allergy blood testing can identify whether mesquite, huisache, Bermuda grass, ragweed, mold, dust mites, or other specific Valley allergens are your triggers, enabling personalized treatment rather than blanket symptom suppression.
March through April and September through October are typically the most challenging periods. Spring brings peak mesquite, live oak, and emerging grass pollen, while fall brings peak ragweed combined with persistent grass pollen. However, Brownsville's subtropical climate means some level of allergen exposure occurs in every month of the year — mold and dust mites are constant due to Gulf humidity.
The top outdoor allergens are mesquite tree pollen (spring), huisache tree pollen (late winter/spring), Bermuda and Johnson grass (March–November), ragweed (fall), and mold spores (year-round). Indoor allergens including dust mites, mold, cockroach, and pet dander are significant year-round concerns. Brownsville's high humidity makes mold a far more persistent problem than in drier Texas cities.
The subtropical climate produces an extremely long growing season, meaning plants produce pollen for most of the year. Gulf of Mexico humidity drives year-round mold growth and creates ideal conditions for dust mites. The flat, open terrain allows pollen to travel long distances. And the Tamaulipan thornscrub ecosystem surrounding Brownsville contains millions of mesquite and huisache trees that produce copious wind-dispersed pollen — a natural allergen source that cannot be controlled.
Effectively yes. Huisache pollinates starting in January, tree pollen peaks March–April, grass pollen runs March–November, ragweed peaks September–October, and mold plus dust mites persist year-round due to Gulf humidity. December is the only month that approaches low allergen levels, and even then, indoor allergens and residual mold remain active.
Yes. HeyAllergy provides telemedicine appointments with board-certified allergists licensed in Texas. Book a virtual consultation, have allergy blood tests ordered to a convenient local 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 Rio Grande Valley triggers — whether mesquite, huisache, Bermuda grass, ragweed, dust mites, or mold. 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.
Yes. Brownsville's resacas — oxbow lakes left by historic shifts in the Rio Grande — create permanent moisture environments throughout the city where mold thrives year-round. Homes near resacas experience elevated humidity and higher mold spore concentrations than homes farther from water. These water features also support vegetation that produces additional pollen and provides habitat for mold-producing organic material.
Brownsville occupies a geographic position unlike any other city in Texas — and arguably in the entire continental United States. Sitting at latitude 25.9°N on the northern bank of the Rio Grande, just miles from the Gulf of Mexico, it is the southernmost city in Texas and one of the southernmost in the country. This extreme southern position places Brownsville at the intersection of four distinct climate zones: the subtropics, the Chihuahuan Desert influence from the west, the Gulf Coastal Plain, and the southern reach of the Great Plains. The result is a unique biome classified as Tamaulipan thornscrub — a dense, thorny subtropical brushland dominated by mesquite, huisache, Texas ebony, and granjeno that extends from Cameron County south into the Mexican state of Tamaulipas. For allergy sufferers, this means exposure to a set of native plant allergens found virtually nowhere else in the United States.
With a population of approximately 186,000 and a predominantly Hispanic community (93.9%), Brownsville is the urban heart of Cameron County and the lower Rio Grande Valley. The city was established following the Mexican-American War, growing around Fort Brown on the Rio Grande. Today, it serves as a major international border crossing, the home of the University of Texas Rio Grande Valley, and a center for the Valley's agricultural economy. Its subtropical character is immediately visible — broadleaf evergreen plants, including the native Sabal mexicana palmetto palm (the only species of trunk-forming palmetto native to Texas), dominate neighborhoods to a degree unmatched elsewhere in the state.
Brownsville's most distinctive geographic feature — and its most significant mold contributor — is its idiosyncratic network of resacas. These oxbow lakes are remnants of the Rio Grande's historic meanders, left behind as the river shifted course over centuries. Unlike seasonal creeks or drainage channels, resacas are permanent water bodies that wind through residential and commercial neighborhoods, creating a web of standing water throughout the city. They provide habitat for wildlife and recreational opportunities, but for allergy sufferers, they represent something more consequential: permanent, distributed moisture reservoirs that support year-round mold growth in a city that already suffers from Gulf-driven humidity.
Homes and businesses built near resacas experience measurably higher ambient humidity than properties farther from water. Mold species including Alternaria, Cladosporium, Aspergillus, and Penicillium colonize the organic material along resaca banks — decaying vegetation, soil, tree bark — and release spores that become airborne on Gulf breezes. During warm, humid months (which in Brownsville means most of the year), resaca-adjacent properties face persistent mold exposure that no amount of indoor air filtration can fully eliminate. Resaca de la Palma State Park, with its 1,200 acres of native semitropical brushland, is both a nationally significant wildlife habitat and an enormous natural mold reservoir that influences air quality for surrounding neighborhoods.
The plant community surrounding Brownsville is fundamentally different from the oak-cedar-pine forests of Central and East Texas, and from the grasslands of the Texas Plains. Tamaulipan thornscrub is characterized by dense stands of thorny shrubs and small trees that have evolved to survive the region's semi-arid conditions while taking advantage of Gulf moisture. For allergists and their patients, the critical species are mesquite and huisache — two prolific pollen producers that define the Valley's allergy profile.
Honey mesquite (Prosopis glandulosa) is the single most common tree in the Rio Grande Valley, growing in virtually every habitat from undisturbed brush country to vacant urban lots to agricultural field edges. It produces wind-dispersed pollen from March through May, with peak concentrations in April that can trigger severe reactions in sensitized individuals. Mesquite pollen is not typically tested for in standard allergy panels designed for Central Texas patients, meaning Valley residents may be suffering from an allergen that hasn't been identified through conventional testing.
Huisache (Acacia farnesiana) is the earliest major tree pollinator in Brownsville, producing its characteristic yellow puffball flowers as early as mid-January. The fine, wind-dispersed pollen fills the air during a season when most Texans aren't thinking about tree allergies. Other native Tamaulipan species — Texas ebony, anacua, retama, sugar hackberry, granjeno, and cedar elm — each contribute to the tree pollen mix at different points in the extended subtropical growing season.
Brownsville's proximity to the Gulf of Mexico creates a humidity profile that fundamentally shapes its allergen environment. Morning relative humidity regularly exceeds 90%, and even afternoon readings typically remain above 60%. This persistent moisture does three things that worsen allergies. First, it creates ideal year-round conditions for outdoor mold growth — mold doesn't have a dormant season in Brownsville the way it does in cities with cold, dry winters. Second, it supports indoor dust mite populations at levels comparable to the most humid cities in the Southeast, without requiring any artificial moisture sources. Third, the humid air itself can irritate already-inflamed airways, compounding the effects of pollen and mold exposure.
The combination of Gulf humidity, subtropical warmth, and abundant organic material from the surrounding thornscrub creates mold spore concentrations that rank among the highest in Texas. Unlike Houston or San Antonio, where mold is a seasonal concern that peaks in fall, Brownsville's mold exposure is a twelve-month reality. After tropical storms and hurricanes — which directly threaten the lower Rio Grande Valley during the June through November hurricane season — flooding and water damage can produce explosive mold growth that affects even homes with no prior mold issues.
Brownsville sits at the center of the Rio Grande Valley's agricultural region, surrounded by farmland producing citrus, vegetables, sugarcane, sorghum, and cotton. This agricultural landscape influences allergy patterns in several ways. Farm operations disturb soil, releasing dust and mold spores into the air. Irrigation canals and drainage ditches create linear moisture corridors where grass, weeds, and mold flourish. Johnson grass — a highly allergenic species — colonizes the margins of agricultural fields and canal banks throughout the Valley, producing heavy pollen loads from spring through fall. Seasonal agricultural burning, while regulated, can produce smoke that irritates respiratory systems already sensitized by allergens.
The flat, open terrain of the Rio Grande Valley — Cameron County has virtually no elevation change — allows wind-borne allergens to travel extraordinary distances. Pollen from mesquite and huisache growing in the brush country west and south of the city reaches Brownsville on prevailing winds. Gulf breezes can carry mold spores and salt spray from the coast. During cold front passages (nortes), which bring sharp temperature drops and strong north winds, allergens can be transported southward from the brush country and agricultural areas north of the Valley.
Brownsville's allergy calendar is among the longest and most continuous of any city in the United States. Huisache tree pollen can begin in January. Tree pollen peaks March through April. Bermuda and Johnson grass pollen runs from March through November — nine months of continuous grass allergen exposure. Ragweed and fall weeds dominate September through November. Mold spores and dust mites persist at high levels year-round due to Gulf humidity. The only month that approaches genuine low-allergen conditions is December, and even then, indoor allergens and residual mold remain active. For residents accustomed to the clear seasonal breaks in allergy exposure that cities farther north provide, Brownsville's relentless subtropical allergen cycle can be overwhelming.
Brownsville's combination of unique subtropical allergens (mesquite, huisache), extremely long grass pollen seasons, persistent Gulf-driven mold, and year-round dust mites creates an allergen environment that overwhelms seasonal antihistamine strategies. Many residents take over-the-counter medications for ten or eleven months of the year without ever achieving genuine relief — because they're fighting a year-round battle with a seasonal weapon.
HeyAllergy offers Brownsville and Rio Grande Valley residents convenient telemedicine access to board-certified allergists and immunologists who understand the Valley's unique subtropical allergen profile. Through a secure video consultation, your allergist can evaluate your symptoms, order comprehensive blood allergy testing at a convenient local lab — including tests for Valley-specific triggers like mesquite and huisache that standard panels may miss — and develop a personalized treatment plan. For patients who qualify, HeyPak sublingual immunotherapy drops can be customized to your specific test results and the allergens endemic to the lower Rio Grande Valley, delivered directly to your home, and taken daily under the tongue. Most patients notice improvement within 3–6 months, with 3–5 years of treatment recommended for lasting relief. Starting at $47/month, HeyPak offers a path to freedom from the Valley's relentless year-round allergen cycle — no needles, no clinic visits, no waitlist.
