Louisiana Allergy Season: The Early, Long, Humid Year

The Louisiana allergy season starts before most of the country has thought about spring, and it refuses to leave on schedule. The Asthma and Allergy Foundation of America (AAFA) placed New Orleans second in its 2025 Allergy Capitals report — No. 2 among the 100 largest metros scored for seasonal allergy burden — and the state's climate explains why. Louisiana pairs an early, warm spring with a long growing season and some of the most persistent humidity in the continental United States, so pollen acts arrive early, overlap generously, and share the stage with mold for most of the year.

New Orleans is the headline, but the pattern is statewide: Shreveport's piney woods, Baton Rouge's oak canopy, and the Acadiana wetlands each run the same long calendar with local accents.

Key takeaways

• The AAFA's Allergy Capitals 2025 report ranked New Orleans No. 2 among 100 US metros for seasonal allergy burden.
• Louisiana allergy season can begin in February with the first tree pollens, weeks ahead of the national spring.
• The Centers for Disease Control and Prevention (CDC) identifies warm, humid environments as prime mold habitat, and Louisiana's Gulf climate keeps outdoor mold elevated for much of the year.
• Pollen Atlas data shows Louisiana's true low season is short: hard frosts are infrequent, so the calendar's break is the briefest in the continental interior.

Louisiana allergy season, act one: the February head start

While the Midwest is still frozen, Louisiana's trees get moving. Oaks — including the great spreading oaks that define New Orleans streetscapes — flower early, joined by elm, ash, and pecan through the late winter and early spring. In New Orleans, the tree season can be underway by February and peaking by March, a full month ahead of the national spring narrative. Pine pollen adds its visible yellow film in the state's pine parishes, dramatic to look at though its large grains are generally considered a minor allergen compared with the hardwoods flowering beside them.

The Gulf comparison

Louisiana's early start is a Gulf Coast pattern with local intensity. Houston runs a similar February-to-March tree build, while Miami operates on the near-tropical calendar described in our Florida allergy season guide. What distinguishes Louisiana within the Gulf group is the combination: early pollen plus river-and-bayou humidity plus a dense hardwood canopy, all inside one airshed.

Act two: grass, heat, and the mold co-headliner

Grass season follows from April into the summer, with Bermuda and other warm-season grasses flowering through the heat. But Louisiana's summer story is as much spore as pollen. The CDC notes that mold grows wherever moisture and organic material meet, and Louisiana supplies both without pause: bayous, wetlands, frequent rain, and vegetation that never fully dries. Outdoor genera build through the warm months, and Pollen Atlas data shows mold signals in Louisiana cities running high on the city rankings well outside the windows northern states associate with mold season.

Rain: relief and release in the same hour

Gulf rain complicates the usual rules. A downpour scrubs pollen from the air for a few hours, a genuine relief northern sufferers would recognize. But in Louisiana the water does not leave: it stands, evaporates, and recharges the humidity that feeds mold, so the day after a storm can trade pollen for spores with little net change in the air's total burden. This seesaw is the state's signature summer pattern, and it is why single-number thinking fails here more than almost anywhere else in the country.

Act three: ragweed into a mild winter

Ragweed arrives in September and runs until the year's first real cold snaps, which in southern Louisiana can hold off into November or December. It overlaps the tail of grass season and the still-elevated mold background, producing the state's characteristic stacked fall. The AAFA's general pollen guidance — that fall weed pollen dominates until frost — applies with a Gulf asterisk: frost is a sometime thing. Northern parishes freeze earlier and get a cleaner break; the coast may see only a handful of cold nights all winter, and warm spells can stir mold readings even in January. Louisiana's off-season is therefore best described as a lull, not a stop.

Reading a long season honestly

The state's lesson for the rest of the country is about duration as a burden in itself. New Orleans's No. 2 ranking in the AAFA's 2025 report reflects scores built from pollen data, medication use, and specialist availability, and Louisiana's contribution to that formula is the calendar's sheer length: more high-burden weeks per year than almost any other state has to offer.

Louisiana's ranking and climate both come with receipts. The AAFA Allergy Capitals hub publishes New Orleans's No. 2 finish in the 2025 report alongside the scoring that produced it. The CDC's mold resources set out the moisture conditions that keep Gulf spores elevated most of the year, and the AAFA's pollen allergy overview covers the pollen side of the state's stacked calendar. Together they describe a place where duration, not any single peak, is the defining allergy statistic.

Frequently Asked Questions

When does allergy season start in Louisiana?

Allergy season in Louisiana can start in February, when the first tree pollens appear in warm years. The tree season typically peaks by March, well ahead of most of the country.

Why is New Orleans ranked No. 2 for allergies?

The AAFA's Allergy Capitals 2025 report ranked New Orleans second among 100 metros scored on seasonal pollen, over-the-counter medication use, and allergist availability. Its early, long pollen seasons and persistent humidity-driven mold underpin the pollen side of that ranking.

Is mold a year-round problem in Louisiana?

Mold is elevated for most of the year in Louisiana because the Gulf climate provides constant warmth and moisture, the conditions the CDC identifies as prime mold habitat. Readings dip in the coolest weeks but rarely disappear entirely along the coast.

When does Louisiana allergy season end?

The season eases after the first cold snaps in late fall, usually November into December, but the break is brief and mild. Tree pollen can resume as early as February, giving Louisiana one of the shortest off-seasons in the country.

Sources: Asthma and Allergy Foundation of America, Allergy Capitals 2025 report; AAFA, Pollen Allergy guidance (2024); Centers for Disease Control and Prevention, Mold resources (2024). This article is general information only. Readers looking for specialists can browse the allergist directory as a directory resource.

Conclusion: duration defines the Louisiana allergy season

The Louisiana allergy season is defined less by any single peak than by accumulation: a February start, overlapping grass and mold through a humid summer, ragweed into a mild winter, and a break measured in weeks. What changes week to week is which of those layers leads, and the daily indexes make that visible at a glance. New Orleans's No. 2 AAFA ranking is the receipt for that arithmetic. Pollen checks you daily. Check it back — free counts and 5-day forecasts, worldwide: PollenAtlas.com