Spring Is Arriving Earlier Across America
While an early spring might feel like a welcome break after a miserable winter, it also brings a cascade of unintended health consequences. All across the U.S., signs of spring (leaf-out, blooms, warmer temperatures) are creeping earlier each year. Climate scientists attribute much of this “spring creep” to rising global temperatures.
For example, data from the National Park Service and USA National Phenology Network show that three-quarters of U.S. parks have experienced earlier springs relative to their historical timing, with half seeing “extreme” acceleration (beyond the 95th percentile of past variation). And in 2025, many regions saw first blooms earlier than the historical average, especially in the eastern U.S. where ocean currents and southerly winds pack a superheated punch.
If these trends continue, leaves could appear nearly three weeks earlier on average by the end of this century compared with mid-20th century baselines.
Health Risks of an Early Spring
Nature is a game of dominos. Every miniscule wobble, when applied at the global scale, can have dramatic effects. Turns out, shifting seasons disrupt the delicate timing of many natural systems—when plants bloom, how much insects breed, and what pathogens thrive. The result? Things like…
1. Longer and Stronger Allergy Seasons
Earlier springs mean earlier blooms, and by default, extended pollen seasons. Research shows that pollen seasons in North America last up to 20 days longer than they were in 1990. What’s more, pollen concentrations have increased by over 20%. Rising carbon dioxide levels also act like fertilizer for many allergenic plants, including ragweed, helping them produce more pollen per plant.
For allergy sufferers, this translates to a longer window of sneezing, watery eyes, and aggravated asthma. Dr. Aaron Bernstein of the Harvard T.H. Chan School of Public Health notes that “plants like ragweed have no problem coming out earlier and producing pollen over multiple cycles now.” With warmer winters, those cycles start sooner and end later each year—creating a perfect storm for seasonal allergy symptoms, symptoms that cause discomfort and distress across the board.
2. More Disease-Carrying Insects on the Move
Warmer temperatures and milder winters allow ticks, mosquitoes, and fleas to survive in areas where they previously couldn’t. That means vector-borne diseases like Lyme, West Nile, and dengue are spreading to new parts of the United States, creeping north from the warmer states resting closer to the equator.
For instance, Lyme disease cases have doubled since the 1990s, with ticks now found in nearly half of U.S. counties. Additionally, mosquito-borne viruses such as West Nile and dengue are appearing earlier in the season and lasting longer into the fall, and chagas cases–a dangerous parasitic infection transmitted by the “kissing bug”–are also rising. These changes raise concern for communities in the Southeast, Great Plains, and Midwest, where warmer, wetter conditions provide prime breeding grounds.
3. The Rising Threat of Untreatable or Emerging Diseases
With insects migrating and reproducing for longer periods, the risk of emerging infectious diseases grows—especially those without reliable vaccines or treatments. While vaccines exist for illnesses like dengue and yellow fever in some regions, others (including Zika and many tick-borne viruses) remain difficult to prevent.
Public health experts warn that warming temperatures could make outbreaks more frequent, pushing healthcare systems to rely on emergency responses—such as broad pesticide spraying or quarantines—that carry their own health and environmental risks.
4. Floods, Contaminated Runoff, and Waterborne Diseases
An early spring can also disrupt water quality. Faster snowmelt, combined with heavier spring rains, often leads to flooding that washes bacteria, chemicals, and waste into waterways. These conditions create ideal environments for waterborne pathogens like E. coli and Vibrio, as well as toxic algae blooms that can contaminate drinking water and seafood.
Such outbreaks can cause gastrointestinal illnesses, skin infections, and liver damage—especially in regions with aging infrastructure or poor drainage systems. Flooding also threatens farmland, leading to crop loss and contamination that ripples through the food supply chain.
In short: When spring arrives ahead of schedule, nature’s calendar falls out of sync with human health. What seems like a harmless (even welcome) change in temperature can heighten allergies, strain state resources, and expand disease risks nationwide.
Supporting Your Health (and the Planet’s) as Seasons Shift
While we can’t control when spring arrives, we can take steps to protect our health and reduce our environmental impact.
- Stay ahead of allergies. Keep an eye on local pollen forecasts, close windows on high-count days, and change air filters regularly. Over-the-counter antihistamines, eyedrops, or allergy shots can also help reduce symptoms.
- Reduce standing water. Eliminate puddles or containers where mosquitoes breed, especially after early rains. Simple actions like unclogging yard drains and emptying birdbaths weekly can help limit disease-carrying insects.
- Support local ecosystems. Plant native flowers, trees, and shrubs that help pollinators thrive despite changing bloom times. Native plants are also more resilient to unpredictable weather. You can search what plants are native to your region by using the National Wildlife Federation’s Native Plant Finder Tool.
- Choose sustainable habits. Eat seasonal produce, reduce food waste, eat a vegan or vegetarian meal a few times a week, and, support local farms, when possible. These actions strengthen food systems that may be stressed by early thaws or floods.
- Spread awareness. Stay informed about how climate patterns affect community health, and encourage others to do the same. Small collective actions—whether in your backyard or through policy support—can make a lasting difference.
Bottom Line
Early springs aren’t just temperature relief or small talk fodder, they signal broader changes in our climate that can affect your health. The heat, bad allergies, bugs, floods–all of these things underscore the importance of being prepared for not only the change of the seasons, but changes to the seasons.
As Dr. Aaron Bernstein notes, “While we can’t attribute a single early spring to climate change with absolute certainty, the broader trends are clear: warming temperatures are reshaping the timing of seasons and the health risks that come with them.”
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This article was updated on October 17, 2025.