Vector Maps: These Maps Show How Early Spring Arrived in Parts of the United States
Spring arrived up to three to four weeks early in parts of the continental United States. The USA National Phenology Network tracks signs of spring across the continental United States based on observations from researchers and through satellite imagery analysis. While parts of this country are experiencing snowstorms well into April, other parts in the south have seen the early arrival of spring.
What is Phenology?
Phenology is the study of the Earth’s cyclical and seasonal phenomenon. As parts of the country emerge from winter, signs of spring show up in the form of new shoots and leaves, the arrival of flowers, and the increased activity of pollinators.
How are the First Signs of Spring Measured?
The National Phenology Network uses two plants to track two early signs of spring: First Leaf and First Bloom indexes. Because they are among the first plants to show their leaves, lilacs and honeysuckles are the two plants used to track the arrival of spring for the First Leaf index. These two plants are also used to track the First Bloom index as lilacs and honeysuckles are also the first plants to bloom and track with early-spring shrubs and leaf out of deciduous trees.
Early Spring in 2020
From year-to-year, NPN tracks these early signs of spring against historical records. This year brought the earliest signs of spring in 39 years for parts of the southeast United States. This map shows where the early arrival of leaves and shoots tracks with the historical record. Areas of North and South Carolina, Louisiana, and Texas are among those seeing its earliest leaf-outs on record.
Less pronounced is the early arrival of First Bloom. In the southeast portion of the United States, the same band of early signs of spring’s arrival stretching from the Carolinas into Texas can be seen but not as much of the early is experiencing the same record breaking early arrival as the First Leaf index.
Map: Where Spring is Arriving Early or Late
This map shows the timing of 2020’s spring season across the lower portion of the continental United States as of April 12, 2020. The “start of spring” for 2020 is compared to the average arrival of spring for each area based on records gathered over the past 39 years (1981-2019). Areas in red are experiencing an earlier than average arrival of spring and areas in blue are experiencing a later than average arrival of spring.
- Status of Spring 2020, USA National Phenology Network
- Gerst, K. L., Crimmins, T. M., Posthumus, E. E., Rosemartin, A. H., & Schwartz, M. D. (2020). How well do the spring indices predict phenological activity across plant species?. International Journal of Biometeorology, 1-13. https://doi.org/10.1007/s00484-020-01879-z