Allergies can happen year-round. But there is a time of year when about 8% of Americans experience the same allergy, nation-wide.

Here's what you need to know about allergy season, when it strikes, and how to prepare.

Allergy season often refers to a specific type of allergy, called allergic rhinitis (or hay fever), that can be triggered by pollen.

Trees, flowers, and grasses typically release pollen in the spring and summer months. However, certain allergies can also happen in the fall, like those caused by weeds.

It all depends on what type of plant you're allergic to and when that plant pollinates. Here's a breakdown of seasonal allergies during the spring, summer, and fall.

Tree pollination begins in February and lasts until June, and grass pollination starts in May and lasts until July.

"The first week of May, when grass pollen starts to surge, is the worst time overall because a lot of people who are allergic to tree pollen are also allergic to grass pollen," says Gary Stadtmauer, MD, FACP, a board-certified specialist in allergy-immunology and internal medicine at City Allergy.

You can also get an idea of how bad your spring allergies may be based on the prior winter.

"Tree pollen tends to be the worst, especially after a prolonged winter when lots of trees bloom in a short space of time," Stadtmauer says. "Unlike grass pollen, tree pollen can rain down thick and the layers can build up on surfaces like cars. Exposure increases dramatically and those who are allergic can have a profound surge in symptoms."

Tree and grass pollination lasts until June or July and ragweed pollination starts in August.

However, summer has generally been considered the least problematic season because plants release less pollen overall during this season.

"Spring has typically been the worst allergy season, and fall is more problematic than summer for those with weed allergies," says Clifford W. Bassett, MD, the founder and medical director of Allergy and Asthma Care of New York.

The most common culprit for fall allergies is ragweed, a plant that grows especially on the East Coast and in the Midwest. Ragweed blooms and releases pollen from August to November, and pollen levels are highest in early to mid-September.

Another common trigger of fall allergies is mold spores. As leaves fall to the ground and other vegetation starts to die, mold can start to grow on that decaying material. The mold then releases spores into the air which can cause allergies for some, says Jay M. Portnoy, MD, director of the Allergy, Asthma & Immunology division at Children's Mercy Hospitals & Clinics.

Other plants that can trigger fall allergies include:

While the timing and severity of allergy season varies across the country, the following climate factors can influence exposure and symptoms:

Climate change has also increased the duration and severity of allergy seasons. "Tree pollen starts earlier, grass pollen extends further into the summertime, and we are seeing more severe ragweed seasons," says Stadtmauer.

The most common symptoms of seasonal allergies are:

If you're not sure what your symptoms are indicating, here's a helpful graphic to differentiate allergy symptoms from the coronavirus, flu, and common cold:

Shayanne Gal/Insider

To prepare for seasonal allergies, we asked Bassett for his tips on how to proactively reduce your exposure to pollen and manage your allergies:

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When is allergy season? Symptoms and treatment for seasonal allergies - Insider - INSIDER