Seasonal allergies, often called hay fever, are triggered by airborne pollen released by trees, grasses, and weeds. Virginia’s climate, characterized by mild winters and a long growing season, prolongs the allergy season compared to colder regions. This means the season often begins much earlier and lasts longer. Understanding when specific allergens dominate the air is necessary due to this extended period of pollen exposure.
Spring Timing and Tree Pollen
The annual pollen season in Virginia typically commences in late February or early March, marking the beginning of tree pollen season. This is often the first and most noticeable phase, sometimes starting earlier following a mild winter. Tree pollen grains are fine and light, allowing them to be carried great distances by the wind and leading to widespread symptoms.
The most common tree allergens include oak, cedar, maple, birch, and pine, with peak activity occurring throughout April and May. An early warm-up can accelerate the reproductive cycle of these trees, while cold snaps can temporarily delay pollen release. This early spring period is characterized by the visible yellow dusting of pollen on cars and outdoor surfaces, indicating high concentrations in the air. The tree pollen season can extend into June before grass pollen takes over.
Summer Timing and Grass Pollen
As tree pollination slows in late May, the allergy season transitions to grass pollen, which typically lasts through mid-July. This shift means that for many sufferers, relief is not immediate once the spring trees finish blooming. The primary grasses responsible for allergic reactions include Bermuda, Kentucky bluegrass, Johnson grass, and Orchard grass.
Grass pollen levels often reach their highest concentration during the late spring and early summer months. This period frequently coincides with high temperatures and humidity, which can intensify respiratory symptoms. Unlike tree pollen, which peaks early in the morning, grass pollen counts often remain high throughout the day, particularly during dry, windy conditions.
Autumn Timing and Weed Pollen
The most intense allergy period arrives in late summer and autumn, driven primarily by weed pollen. This phase begins around mid-August and persists until the first hard frost, typically occurring in late October or early November. The season’s duration depends directly on temperature, as frost kills off the pollen-producing weeds.
Ragweed is the most significant allergen during this time, with a single plant capable of producing up to a billion pollen grains. These minute, lightweight grains are easily dispersed by the wind and can travel for hundreds of miles. The pollen counts for ragweed frequently peak around Labor Day and mid-September, causing severe symptoms for the allergic population.
The damp, cooling conditions of autumn also contribute to an increase in outdoor mold spores, which often overlap with the ragweed season. Molds like Alternaria and Cladosporium thrive in decaying vegetation, such as piles of fallen leaves, releasing spores into the air. This combination of weed pollen and outdoor mold lasts until the first major freeze effectively ends the seasonal pollen cycle.
Year-Round Allergy Factors
While pollen dictates the seasonal rhythm, many people experience persistent symptoms due to year-round indoor allergens. Virginia’s high humidity levels create an environment conducive to the proliferation of non-seasonal irritants. These allergens remain problematic, especially during winter when homes are sealed and ventilation is limited.
Dust mites are a major concern, as they thrive in the warm, humid conditions prevalent throughout the year and are concentrated in bedding and carpets. Pet dander from cats and dogs also causes continuous allergic reactions indoors. Indoor mold, often distinct from seasonal outdoor varieties, can develop in damp areas of the home, such as bathrooms, basements, or air conditioning systems. Maintaining indoor humidity below the 60% threshold is recommended to help control the growth of these household allergens.