Spring has brought increased pollen levels across the Western and Southern United States, significantly impacting millions of Americans with seasonal allergies. The Asthma and Allergy Foundation of America reports that pollen seasons have lengthened by an average of 20 days between 1990 and 2018, primarily due to climate change, leading to more intense and prolonged allergy symptoms for approximately 106 million Americans. Tree, grass, and weed pollen are the main culprits, with rising temperatures expected to exacerbate the situation. AccuWeather's 2026 U.S. allergy forecast predicts high tree pollen levels moving north from the South and Ohio Valley, affecting more than 29 states.