Seasonal allergies occur when your immune system overreacts to allergens in the air, such as outdoor molds and pollen from trees, grasses, or weeds.
Symptoms of seasonal allergies may include sneezing, congestion, itchy eyes, coughing, and a runny nose.
The length of allergy seasons can depend on where you live. Knowing when allergy seasons occur can help you manage your symptoms and lower the impact of allergies in your daily life.
Allergy seasons tend to follow a general pattern. May is the peak month for high pollen in the United States. You can experience seasonal allergies year-round if you live in warmer areas, though specific pollen peaks may vary by plant species and weather patterns.
Allergy season timelines in the U.S. by season are:
- Winter: Winter usually offers a break from allergy season, but it’s not pollen-free everywhere. In warmer southern states, certain trees, such as cedar and oak, may release pollen early.
- Spring: Tree pollen peaks from March through May. Trees like oak, birch, and maple release large amounts of pollen during this time, particularly in the northern and central U.S. In warmer regions, tree pollen can start as early as February and linger into the early summer.
- Summer: Grass pollen peaks in late spring and continues through early summer. Regions with long summers or mild climates may have a longer grass pollen season.
- Fall: Ragweed, a common wild weed, is the primary allergen during the fall allergy season, which lasts from August through October or November.
Several factors influence allergy seasons and symptoms, including location, weather patterns, climate, and air pollution.
Geographic Location and Climate
Your location and its climate (average local weather conditions over 30-plus years) affect when allergy season happens and how long it lasts. Different regions also have different pollen-producing plants, which bloom and release pollen at various times of the year.
Spring allergies can begin as early as late February in areas with mild winters, while regions with longer, colder winters might experience shorter allergy seasons. In warmer regions, allergy seasons can last year-round because various plants, such as grasses, can pollinate all year.
Weather
Weather plays a role in the severity and length of seasonal allergies. Some weather patterns that can affect allergy seasons include:
- Rain: Rain can temporarily relieve allergies by washing pollen out of the air, but it can also raise allergens once the rain stops and plants release a burst of pollen.
- Wind: High winds can carry pollen over long distances and stir up dust and other particles, adding to the allergens in the air.
- High temperatures: Warm, rainy spring weather encourages plant growth, which can make allergy seasons longer and more intense.
- Humidity: High humidity can create favorable conditions for mold growth, another common allergen that can worsen your seasonal allergy symptoms.
Air Pollution
Areas with more air pollution often experience more days with higher pollen counts, leading to a longer allergy season. Airborne pollutants can mix with pollen, creating a stronger allergen that triggers a more intense immune response, worsening your allergy symptoms.
Climate Change
Rising temperatures and changing rainfall patterns from climate change can extend growing seasons, allowing plants to release pollen at unexpected times and in larger amounts.
Warmer winters can cause trees and grasses to start pollinating earlier, and longer summers give plants more time to release allergens into the air. Increased carbon dioxide levels, a major contributor to global warming, are also linked to higher pollen production, making the season longer and more severe.
Botanical Sexism
Botanical sexism refers to the practice of planting more male trees than female trees in urban areas, which has unintentional consequences for people with allergies.
Male trees tend to produce more pollen, as their primary role is to fertilize female trees. Many cities favor planting pollen-producing male trees rather than fruit- or seed-bearing female trees, which leads to more pollen in the air.
Urban Heat Islands
Cities often experience the urban heat island effect, where built-up areas, roads, and buildings trap heat and raise local temperatures more than in rural areas.
This warmer environment can lead to plants blooming earlier, longer growing seasons, and prolonged pollen production. These effects, along with increased air pollution exposure, mean city residents may experience allergy symptoms earlier in the season and longer than those in cooler rural areas.
Common allergy triggers vary by season because different plants release their pollen at specific times. The timing and types of allergens depend on the local climate and the plants that grow there, so your allergy triggers can change throughout the year.
Spring Allergy Season
Tree pollen is responsible for most spring seasonal allergies. Spring allergy season typically begins in late February and lasts until late May.
Some trees produce visible, heavy pollen that falls near the tree, creating yellow dust that can cover outdoor structures. Other trees produce smaller, invisible pollen that quickly travels with the wind and enters the eyes, nose, and airways, causing allergy symptoms.
Trees that tend to cause the most allergies throughout the U.S. include:
- Ash
- Cedar
- Maple
- Mulberry
- Oak
- Pecan
- Walnut
- Willow
Summer Allergy Season
Grass and hay pollens cause most summer allergies, commonly known as hay fever. The summer allergy season usually lasts from April through June, though it can last year-round in warmer regions.
Grass pollen is a lightweight, powder-like substance that spreads in the wind. Grass pollen is at its heaviest in the air early in the morning after the dew dries and after it rains.
All grasses can cause allergies, including:
- Bahai
- Bermuda
- Fescue
- Johnson
- Kentucky blue
- Rye
- Timothy
Fall Allergy Season
Ragweed is the dominant fall allergen, particularly in the Midwest and the East Coast, and a leading cause of seasonal allergies. Its pollen is made of tiny particles that float through the air.
Fall allergy season lasts from August through November, peaking in September and October. One ragweed plant can produce up to 1 billion pollen grains, which can enter your mouth, nose, or eyes and cause allergy symptoms.
Winter Allergy Season
Winter doesn’t typically have any major allergy triggers because, in many parts of the U.S., pollen isn’t as active during the winter months, and most winter allergies take place indoors.
However, in areas with milder winter seasons where grass can pollinate year-round (e.g., several states in the South), allergy season can start as early as February. Certain trees found in the South, such as cedar, juniper, cypress, birch, cottonwood, and acacia, can also cause seasonal allergies during winter months.
Common allergy triggers in the winter include:
- Pet hair and dander
- Dust and dust mites
- Mold
- Certain insect and rodent waste
Living with seasonal allergies can be frustrating, but with the right strategies and treatments, you can find relief and ease your symptoms.
You can help keep your allergies under control if you:
- Monitor pollen counts and forecasts: Regularly check the local pollen forecast so you can plan your outdoor activities accordingly. Many weather websites, regional news outlets, and apps provide daily or weekly updates on pollen counts and forecasts. On high-pollen days, try to limit outdoor exposure, especially in the early morning when pollen levels are typically highest.
- Reduce exposure to allergens: Keep windows closed during peak pollen times, and consider using high-efficiency particulate air (HEPA) filters in your home to remove air particles that can trigger allergies. After spending time outdoors, change your clothes and shower to remove any pollen that may have clung to your body.
- Try nasal rinses: Saline rinses can help flush pollen, dust, and other allergens from your nasal passages, relieving congestion. This simple, natural method can help reduce symptoms and is safe to perform daily.
- Consider treatments: Over-the-counter (OTC) and prescription medications can help manage allergy symptoms. Antihistamines like Claritin (loratadine), decongestants, or nasal sprays can help relieve sneezing, congestion, and itchy eyes. If you know which season(s) cause your allergies, taking medications two weeks before allergy season begins can help reduce symptom severity. Talk to a healthcare provider to determine the most effective treatments for your symptoms.
Allergy seasons can vary by region, with warmer climates experiencing longer or year-round exposure to allergens.
The peak allergy season, where most people will experience symptoms, typically starts in March and ends in May.
If you live with seasonal allergies, monitoring local pollen counts, reducing allergen exposure, and discussing treatments with your healthcare provider can help you avoid symptoms.
