When Do Seasonal Allergies Start?

Seasonal allergies affect millions of people worldwide. These allergies are triggered by specific allergens that are prevalent during certain times of the year in your region. When are seasonal allergies at their peak in your area? That depends on a wide variety of factors ranging from climate to local flora.

When do seasonal allergies start?

In this article, we’re discussing when seasonal allergies typically begin in different regions. We’ll also identify common seasonal allergens and explain why these allergies vary by location and time of year.

Common Seasonal Allergens

Before answering the question, “When do seasonal allergies start?” it’s helpful to identify common seasonal allergens as well as your specific triggers Identifying your allergies is the first step toward your proper diagnosis and subsequent allergy treatment plan. 

• Tree pollen: Pollen from oak trees, birch trees, cedar trees, and more are frequently the source of spring seasonal allergies.
• Grass pollen: Grasses like Bermuda grass, Timothy grass, and Kentucky bluegrass (also called Meadow grass) are common triggers for spring and summer allergies.
• Weed pollen: Certain weed species — including ragweed, sagebrush, and lambs quarters (part of the goosefoot family) — release pollen in the late summer and fall, contributing to seasonal allergies. Ragweed allergy symptoms are the most prominent fall allergies, especially hay fever (seasonal allergic rhinitis).
• Mold spores: Mold spores are tiny airborne particles released by molds, which can grow indoors and outdoors. They can trigger allergies year-round but are often more prevalent in humid summer and early fall seasons in your region.

Allergy Testing: Not all at home allergy tests are created equal. We offer an allergy test kit analyzed by a CLIA-certified lab to provide accurate test results for 40 indoor and outdoor allergens. We also accept uploads of previous allergy test results. If you prefer in-person testing, we offer that at our allergy clinic in NYC or you can do it  at a laboratory like Quest or Labcorp.

When Do Seasonal Allergies Start Where I Live?

We’ve previously discussed how long seasonal allergies last, but when do seasonal allergies start for your region? Familiarizing yourself with the major seasonal allergens in your area is paramount to effective preparation and treatment.

Different allergens can have elevated levels across periods of the year, however, each region has its own major time of year where the highest number of seasonal allergens are prevalent. It’s easiest to break it down by region of the United States to help you identify when you may experience these symptoms most.

1. Midwest
2. Northwest
3. Northeast
4. South Central
5. Southeast
6. Southwest

1. Midwest Region

Tree pollens start in March, with grass and weed pollens around May.

The Midwest of the United States commonly has high levels of grass pollen around May and extending through the summer into early fall. If you live in this region, you may also experience elevated tree pollen levels in the spring months typically starting in March and continuing until replaced by seasonal grass and weed pollens.

2. Northwest Region

Tree pollens from September to April, with grass and weed pollens beginning in May.

The Northwest of the country also experiences a wide variety of grass pollen allergens starting around May and extending into early September. Elevated tree pollens from cedar trees begin in the Northwest region around September and extend into the early spring, typically until March.

3. Northeast Region

Tree pollen allergens are most heavy from March to July, and grass and weed pollens are elevated starting in May.

The Northeast region also has periods of heavy tree pollens that shift to higher seasonal grass pollen allergen levels as the year continues. Trees like oak, walnut, and sycamore release higher pollen levels starting in March. This region also has a heavy prominence of juniper tree pollens in the fall and spring months, starting in September and continuing through March similar to the Northwest.

Grass and weed pollens like Bermuda grass, ragweed, and sagebrush usually begin in May, June, or July.

4. South Central Region

Tree pollen levels are elevated in April (cedar and juniper in October), with grass and weed pollen levels increasing in May and June.

When are seasonal allergies most prevalent in the South Central region? Similar to other parts of the country, you’re most likely to see local tree pollen levels highest beginning in April. This mostly applies to trees like elm, oak, and maple, which have particularly high pollen levels in the Dallas, Texas area. Cedar allergies are also extremely prevalent in the South Central region, in some cases being so severe it’s referred to as “cedar fever.”

Grass and weed pollens like Bermuda grass, plantain weed, and ragweed begin their highest seasonal levels in May and June. These continue through the summer and into the fall.

5. Southeast Region

Tree pollens begin in February and March, with grass and weed pollens higher starting in April.

The Southeast has a notably higher number of seasonal allergens throughout the year. Some of this, including elevated mold spore levels, is due to higher humidity.

Tree pollens begin a little earlier than in other parts of the country, with cedar and pine starting in February. Grass and weed pollens also start a little earlier here, climbing to higher allergen levels beginning in April. As humidity is a favorable climate factor for mold spores, these are high in the Southeast region during the summer months.

6. Southwest Region

Higher tree pollens in March, with grass and weed pollens elevating in June.

If the Southeast has the highest average number of seasonal allergens, the Southwest arguably has the fewest. This doesn’t mean they don’t exist, however, with tree pollens like elm and oak starting their highest levels in March. Elevated grass and weed pollen levels for ragweed and rye begin a little later here, typically starting their highest levels in June.

When do seasonal allergies start where I live? The answer to this common question varies in onset and intensity depending on your region and the specific environmental factors. Understanding when seasonal allergies start in your area and identifying which you’re sensitive to can help you manage your allergy symptoms more effectively. Consult with a doctor or allergist for an accurate diagnosis and to develop your allergy treatment plan.