While the first day of spring arrives on March 20, many places across the United States see their first signs of the season much sooner. The Spring First Leaf Index, provided by the USA National Phenology Network, tracks when and where the first signs of spring appear.
Map of the progress of spring, showing when and where the first signs of spring appear, also known as 'first leaf' or 'leaf out'. Areas where spring is arriving early, compared to the long-term average, are shown in orange while areas where the start of spring is arriving late are shown in purple. The number of days early or late is found by taking the difference between this year's first leaf date (Spring First Leaf Index) and the first leaf date from the 30-Year Average Spring Index, both produced by the USA National Phenology Network. These indices are created using ground-based observations for species active in early spring, like lilac and honeysuckle, combined with temperature and weather event data from the National Centers for Environmental Prediction (NCEP) and PRISM. Explore more ways to visualize this data.
At first glance, this Spring Leaf Index may look like orange and purple stripes creeping northward across the country. In reality, it’s a reflection of temperature conditions in the months leading up to when the first leaves of spring occurred in each location. Before the first leaves of the season can appear, a certain amount of warmth needs to accumulate.
Leaf buds on the common lilac (Syringa vulgaris). The USA National Phenology Network's Spring indices are created using ground-based observations for species active in early spring, like lilac and honeysuckle. Photo taken April 1, 2012 by oddharmonic on Flickr. Used under Creative Commons license CC BY-SA 2.0.
Typically, the southernmost portions of the United States see their first leaves around mid-January. This year, the first signs of spring arrived right on time in Miami, FL, with temperatures near normal when the first leaves appeared around January 14.
However, the mild temperatures didn’t last long. A cold spell swept across the southern U.S. in late January. The frigid temperatures fueled a historic snowstorm along the Gulf Coast, and caused the first signs of spring to arrive up to 10 days later than usual in places such as Houston, TX, New Orleans, LA, and Jacksonville, FL.
Graph showing how much cooler or warmer than average it was in Houston, TX in January 2025. The graph also marks the date when the first signs of spring appear (also known as 'first leaf' or 'leaf out') on average (January 22), as well as when it occurred this year (January 31). Colder than average temperatures led to spring leaf out arriving as much as nine days late. To check on the arrival of spring at a different location, visit the USA National Phenology Network's visualization tool.
Just as quickly, temperatures swung back the other way in early February and were above normal in the Southeast. Locations such as Atlanta, GA, and Charlotte, NC, saw their first leaves of spring arrive about four to six days early thanks to this warm spell.
Graph showing how much cooler or warmer than average it was in Charlotte, NC in February 2025. The graph also marks the date when the first signs of spring appear (also known as 'first leaf' or 'leaf out') on average (February 16), as well as when it occurred this year (February 11). Warmer than average temperatures led to spring leaf out arriving as much as five days early. To check on the arrival of spring at a different location, visit the USA National Phenology Network's visualization tool.
The first signs of spring continued to move northward through mid-March as central and eastern portions of the U.S. experienced above-normal temperatures. Record warmth in Pittsburgh, PA, allowed the first leaves of spring to emerge around 8 days early. However, there are hints at a swing back to cooler temperatures in late March, when places like Cleveland, OH, would typically expect to see their first signs of spring.
Graph showing how much cooler or warmer than average it was in Pittsburgh, PA in March 2025. The graph also marks the date when the first signs of spring appear (also known as 'first leaf' or 'leaf out') on average (March 25), as well as when it occurred this year (March 17). Warmer than average temperatures led to spring leaf out arriving as much as eight days early. To check on the arrival of spring at a different location, visit the USA National Phenology Network's visualization tool.
Stay tuned: in upcoming posts, we'll explore how the timing of spring's arrival is shifting in response to changing climate patterns.