Environmental Allergies through the Seasons

Environmental allergies happen when your body overreacts to an allergen like mold, pollen, or dust mites. This can cause symptoms like itchy watery eyes, sneezing, and a runny or stuffy nose. Different allergens can be more common at certain times of the year.^1,2

The exact month when plants bloom or the frost comes can depend on your climate. Also, different years will have different weather patterns, which impacts plants. For example, if you have a very long and cold winter, allergy season may be shorter. But, in general, certain environmental allergens are worse at certain times of the year.^1-3

Spring flowers bring pollen allergies

Springtime brings the start of the growing season. As the temperature rises, plants start to bloom and release pollen. Tree allergies to oak, elm, maple, and birch are some of the most common in the United States. Tree pollen season is usually from around February through June.^1,2

Grass pollen season also starts in spring. Some common grass allergies are to Bermuda grass, Kentucky bluegrass, and Bahia grass. Grass pollen season lasts from May to early July.¹

Summer heat and ragweed allergens

Trees and grass also continue to bloom and release pollen through the summer. After levels of pollen from grass and trees start to fall, you may have a short break. But then weed pollen season starts in early August and continues until the first frost. The most common weed allergy is to ragweed.^1,2

Mold season typically peaks between spring and summer in June. Mold spores are tiny seeds for fungi. Spores are very small and drift through the air. They spread best in humid or windy conditions. Mold can be around through the summer until the first frost.^1,2

Summertime weather can also impact your allergies. Hot humid air can carry higher concentrations of allergens. This can make symptoms worse. Thunderstorms, which are more common in summer, can also spread pollen. The heavy wind and rain from the storm spread the pollen and can cause a sudden onset of allergy symptoms.¹

Fall windy weather brings weed pollens

All the spring and summer allergens will carry over into fall, especially mold and ragweed. Weed pollen is very high and peaks during fall. Windy fall weather can also spread allergens around. Luckily, pollen and mold counts start to fall around the first frost. The frost keeps plants from blooming and producing more pollen.^1,2

Winter indoor allergies

Wintertime can bring some relief from plant pollen, but some people may experience other allergies. In the cold winter months, people are more likely to spend time indoors. If you are allergic to indoor allergens like dust mites or pet dander, you may have more exposure. Mold can also thrive in damp indoor conditions. Consider buying a high-efficiency particulate air (HEPA) filter to keep your indoor air clean.^1,4

In warmer climates, tree pollen season can start at the end of winter. As the climate continues to change, this may become common in more places.^2,5

Impact of a changing climate

Seasonal allergies tied to warm weather are starting to last longer. Climate change is causing longer and worse allergy seasons. Since 1990, the US freeze-free season has increased by about 20 days. This is the time of the year with no freezing when plants can grow. A longer freeze-free season means a longer allergy season. Across the United States, allergy season now produces about 20 percent more pollen.^2,5