Longer Allergy Season: Climate Change & What to Expect in 2024

For many Americans, the telltale signs of spring – warmer temperatures and blooming trees – are arriving with an unwelcome guest: an early and potentially more intense allergy season. Tree pollen levels are already climbing across much of the country, prompting concerns that sneezing, coughing, and watery eyes will begin sooner and last longer than usual. This shift isn’t simply anecdotal; recent analysis indicates a clear trend toward lengthening allergy seasons, driven largely by the effects of a changing climate.

A latest analysis from Climate Central reveals that the frost-free growing season has extended by an average of 21 days since 1970 in at least 173 U.S. Cities. This extended growing season provides plants with more time to produce and release allergy-inducing pollen. “Over the last 50 years or so, the time between the last freeze and the first freeze has gotten longer, so there’s essentially a longer growing season when plants generate the pollen that causes allergies,” explains Kristy Dahl, PhD, vice president for science at Climate Central. And it’s not just the duration of the season that’s changing; the amount of pollen being produced is similarly increasing, with estimates suggesting a 20 percent rise.

Early Arrival Across the Country

The early start to allergy season is particularly noticeable in several regions. The USA National Phenology Network, which collaborates with Climate Central, reports that tree pollen is arriving three to five weeks earlier than expected in Colorado, Kansas, and the Northern Great Plains – including parts of Montana, Nebraska, North Dakota, South Dakota, and Wyoming. This initial spread of pollen is also occurring 10 to 20 days ahead of schedule along the Gulf Coast and much of Oklahoma. Southern California and southern Arizona are also experiencing an early onset of tree pollen season, according to AccuWeather’s Allergy Forecast.

However, the picture isn’t uniform across the country. Some areas, like Georgia, the Carolinas, and Virginia, are experiencing a delayed spring due to colder temperatures, resulting in a one-to-two-week delay in pollen release. AccuWeather cautions that even a late spring frost may only offer temporary relief, as pollen levels can rebound intensely once warmer weather returns. The Ohio Valley is currently predicted to be one of the hardest-hit regions this year following spring rainfalls.

Northwest Sees the Most Dramatic Changes

The Northwest is experiencing some of the most significant changes in allergy season length. Dr. Dahl notes, “We’re seeing some of the biggest increases in pollen in the Northwest where the growing season has expanded by 31 days since 1970.” The region’s already mild climate makes it particularly susceptible to the effects of a warming trend, leading to a longer period of pollen production.

The Climate Connection: More Than Just Warmer Temperatures

The underlying driver of these changes is, according to Dr. Dahl, climate change. “It’s a clear signal of a warming world, driven by carbon pollution,” she states. The increase in atmospheric carbon dioxide doesn’t just warm the planet; it also acts as a kind of fertilizer for plants, enabling them to produce more pollen. This effect is supported by research published in Nature, which projects that warmer temperatures could increase annual total pollen emission by 16–40% by the end of the century, with potential increases of up to 200% if atmospheric CO2 levels double.

The Nature study also highlights that the timing of pollen release is shifting, with spring emissions starting 10–40 days earlier and summer/fall weed and grass emissions starting 5–15 days later. These phenological shifts – changes in the timing of biological events – vary depending on the plant species, leading to complex patterns of pollen release across different regions.

What This Means for Allergy Sufferers

The implications of these changes are significant for the millions of Americans who suffer from seasonal allergies. Longer allergy seasons and increased pollen levels can lead to more frequent and severe symptoms, impacting daily life and potentially exacerbating other conditions like asthma and eczema. Juanita Mora, MD, an allergist with the Chicago Allergy Center, warns, “This is going to be a really tough time for those with allergies.”

For those particularly vulnerable, experts recommend starting allergy medications (antihistamines, nasal sprays, inhalers) two to three weeks before the typical start of allergy season in their region. Nana Mireku MD, a pediatric allergist with TexasAllergyMD, emphasizes that these medications are most effective when they’re already active in the system before pollen counts peak.

Practical Steps for Managing Allergy Symptoms

Beyond medication, several practical steps can help manage allergy symptoms:

• Maintain windows closed, especially while sleeping and driving.
• Shower and change clothes after spending time outdoors.
• Monitor local pollen counts and limit outdoor exposure on high-pollen days.
• Consider allergy testing to identify specific triggers.
• Use saline rinses, nasal steroid sprays, and antihistamines as directed.
• Explore allergen immunotherapy (allergy shots or sublingual tablets/drops) for long-term relief.

Looking Ahead: A Call for Action

The lengthening allergy season is not simply a matter of discomfort; it’s a tangible consequence of a warming planet. Addressing this issue requires a broader effort to mitigate climate change by reducing carbon emissions. Dr. Dahl urges a transition away from fossil fuels like coal, oil, and gas to minimize the long-term impact on public health.

While systemic change is crucial, individuals can also take steps to prepare for increasingly challenging allergy seasons. Proactive management of symptoms, combined with awareness of regional pollen trends, can help minimize the impact of this growing environmental health concern. The American College of Allergy, Asthma, and Immunology offers resources and guidance for managing allergies and asthma, including finding a board-certified allergist in your area.