Pollen: Spring Pollen Season is Getting Longer & More Intense

Pollen: Spring Pollen Season is Getting Longer & More Intense
This map from the USA National Phenology Network (USA-NPN) shows when springtime activity in plants typically began over the last 30 years

Figure: This map from the USA National Phenology Network (USA-NPN) . The start of spring occurs on the date when enough heat has accumulated to initiate growth (leafing and flowering) in temperature-sensitive plants. The United States Global Change Research Program uses data from the USA-NPN Network as an indicator for start of the spring season.

Our changing climate has caused shifts in precipitation patterns, more frost-free days, warmer seasonal air temperatures, and more carbon dioxide (CO2) in the atmosphere. These changes may lead to both higher pollen concentrations and earlier and longer pollen seasons. Overall, data from the USA National Phenology Network (shown on the map to the left) indicates that on average, the start of spring has occurred earlier in the contiguous United States since 1984. found that nationwide, total pollen amounts increased up to 21% between 1990 and 2018, with the greatest increases recorded in Texas and the Midwest. One study shows where the pollen monitoring stations are located across the country.

Start of Spring Across the United States as of May 1, 2024
This map from the USA National Phenology Network (USA-NPN) shows when springtime activity in plants typically began over the last 30 years based on pollen monitoring stations certified by the American Academy of Allergy, Asthma & Immunology National Allergy Bureau. The start of spring occurs on the date when enough heat has accumulated to initiate growth (leafing and flowering) in temperature-sensitive plants.

 

Figure: This map depicts where springtime biological activity began earlier than average (red tones) and later than average (blue tones) this year. We can expect an earlier start to the pollen season in regions experiencing an earlier than normal start to spring. For more information, visit the USA-NPN Status of Spring page