Hay fever, or allergic rhinitis, is an immune overreaction to airborne allergens like pollen, dust mites, or pet dander. It causes nasal and eye symptoms but, despite the name, no actual fever.

How common is hay fever?

Very. CDC reported diagnosed seasonal allergy in 25.7% of US adults and 18.9% of children in 2021.

What is the difference between seasonal and perennial hay fever?

Seasonal hay fever is triggered by pollen and outdoor mold on a yearly cycle. Perennial hay fever runs year-round and is usually caused by indoor allergens such as dust mites, pet dander, and mold.

What triggers hay fever in each season?

Tree pollen in early spring (about February to April), grass pollen from mid-April through summer, and ragweed and other weeds from late summer to the first frost.

Does rain help or hurt hay fever?

Both. Rain temporarily clears pollen from the air, but it can also break grains into smaller fragments that spread, and storms occasionally cause sharp symptom spikes.

What is thunderstorm asthma?

A rare event where storm humidity ruptures grass pollen into tiny particles that reach deep airways. The 2016 Melbourne outbreak saw pollen rise about 250% and was tied to 10 deaths.

Hay Fever (Allergic Rhinitis): Causes, Seasons, and Relief

Hay fever, or allergic rhinitis, is an immune overreaction to airborne allergens. Despite the name there is no hay and no fever. It is common: CDC data put diagnosed seasonal allergy at 25.7% of US adults and 18.9% of children in 2021, making it the most prevalent allergic condition in kids.

Hay fever comes in two forms. Seasonal hay fever is driven by tree, grass, and weed pollens (and outdoor mold) on a yearly cycle. Perennial hay fever runs year-round and usually traces to indoor triggers such as dust mites, pet dander, or mold (per ACAAI).

Hay fever tracks the pollen calendar

Allergic rhinitis flares whenever your trigger is airborne — tree in spring, grass in summer, ragweed in fall.

JFMAMJJASOND

TreeMar–May

GrassMay–Jul

RagweedAug–Oct

Tree, grass, and ragweed shading is Weather Story’s deterministic seasonal-estimate model (regional AAFA/ACAAI season windows; see methodology), not measured pollen counts. Darker = higher typical intensity.

The three pollen seasons

Seasonal symptoms follow a predictable relay. Tree pollen comes first, roughly February through April (earlier in the South). Grass pollen takes over from mid-April through summer. Ragweed and other weeds close the year from late summer to the first frost. Where these windows overlap, or in mild climates where they barely pause, symptoms can run for many months.

Symptoms

Typical hay fever symptoms include nasal congestion, a runny nose and post-nasal drip, sneezing, and itching of the nose, mouth, eyes, or throat. Many people also get red, watery eyes, puffy eyelids, a lingering cough, and fatigue from disrupted sleep. The pattern tends to track the pollen calendar for whichever allergen you react to.

Hay fever is not the same as a cold. The hallmark is itching — of the eyes, nose, and throat — which colds rarely cause, and symptoms persist for weeks rather than resolving in a week or so. If your "spring cold" returns at the same time every year, hay fever is the more likely explanation.

How weather moves pollen

Weather is a strong lever on pollen. Warm, dry, windy days lift counts; rain knocks pollen down, at least briefly. The twist is that storms can backfire: rain can shatter pollen grains into smaller fragments that spread, and in rare "thunderstorm asthma" events, humidity ruptures grass pollen into particles small enough to reach deep airways. The 2016 Melbourne event saw airborne pollen jump about 250% and was linked to 10 deaths (per published case reviews and Cleveland Clinic).

Finding relief

Managing hay fever is a layered job: know when your pollen is high, cut exposure, and treat symptoms. Intranasal corticosteroid sprays are the most effective single medication, and second-generation antihistamines help most when sneezing and itching lead. Keep windows shut during peak weeks, run AC, and shower after being outdoors. If medication and avoidance are not enough, an allergist can test for your specific triggers and offer immunotherapy, the only treatment that changes the underlying allergy.

How common hay fever is

25.7%

of U.S. adults have seasonal allergy

CDC/NCHS 2021

18.9%

of U.S. children have seasonal allergy

CDC/NCHS 2021

+250%

pollen spike a thunderstorm can trigger

Cleveland Clinic

Check your local pollen forecast

Pollen seasons vary sharply by region. These metros see some of the worst pollen pressure — check the current forecast for each, or look up any US city on the pollen count hub:

Scranton, PA pollen count — A Northeast valley that traps tree, grass, and ragweed pollen through a long season.
Wichita, KS pollen count — Plains location stacks grass and ragweed seasons on top of spring trees.
Richmond, VA pollen count — Mid-Atlantic warmth stretches tree, grass, and ragweed seasons across much of the year.
Oklahoma City, OK pollen count — Southern Plains winds carry grass and weed pollen through a long warm season.
Memphis, TN pollen count — Mid-South humidity and a long growing season keep multiple allergens airborne.
New Orleans, LA pollen count — Gulf warmth means little winter dormancy, so pollen and mold run nearly year-round.

Frequently asked

What is hay fever?: Hay fever, or allergic rhinitis, is an immune overreaction to airborne allergens like pollen, dust mites, or pet dander. It causes nasal and eye symptoms but, despite the name, no actual fever.
How common is hay fever?: Very. CDC reported diagnosed seasonal allergy in 25.7% of US adults and 18.9% of children in 2021.
What is the difference between seasonal and perennial hay fever?: Seasonal hay fever is triggered by pollen and outdoor mold on a yearly cycle. Perennial hay fever runs year-round and is usually caused by indoor allergens such as dust mites, pet dander, and mold.
What triggers hay fever in each season?: Tree pollen in early spring (about February to April), grass pollen from mid-April through summer, and ragweed and other weeds from late summer to the first frost.
Does rain help or hurt hay fever?: Both. Rain temporarily clears pollen from the air, but it can also break grains into smaller fragments that spread, and storms occasionally cause sharp symptom spikes.
What is thunderstorm asthma?: A rare event where storm humidity ruptures grass pollen into tiny particles that reach deep airways. The 2016 Melbourne outbreak saw pollen rise about 250% and was tied to 10 deaths.