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Status of Spring
How do you know when spring has begun? Is it the appearance of the first tiny leaves on the trees, or the first crocus plants peeping through the snow? The First Leaf and First Bloom Indices are synthetic measures of these early season events in plants, based on recent temperature conditions. These models allow us to track the progression of spring onset across the country.
How does this spring compare to "normal"?
June 6, 2022
Our spring leaf anomaly compares the arrival of spring leaf out this year to a long-term average of 1991-2020. In the East, spring leaf out was patchy this year, arriving days to weeks late across much of the Southeast and upper Midwest, and arriving days to weeks early across the southern part of the Midwest, the Southern Appalachians, the mid-Atlantic, and the Northeast. In western states, spring leaf out was also patchy, arriving a week late in some locations and over a month early in others. Parts of Montana and South Dakota were 2-3 weeks early.
Spring bloom has arrived at all but the highest elevation locations in the West. Spring bloom arrived days to a week late in Texas and Florida and days to several weeks early in California. Spring bloom is over a week early in parts of Georgia, the Carolinas, and Virginia. The mid-Atlantic was patchy, several days early in some locations and several days late in others. The southern part of the Midwest was several days to a week late.
How often do we see a spring this early or late?
How typical was this year’s spring? Darker colors represent springs that are unusually early or late in the long-term record. Gray indicates an average spring.
In parts of California and Arizona, this year's spring leaf out is the earliest in the 40-year record (dark green). In parts of the Dakotas, Minnesota, and Wisconsin, this year's spring leaf out is the latest on record (dark purple).
In parts of Texas, this year's spring bloom is the latest on record (dark purple).
When did spring arrive at locations across the country?
The First Leaf Index map at right shows locations that have reached the requirements for the Spring Leaf Index model so far this year.
The First Bloom Index map at right shows locations that have reached the requirements for the First Bloom Index model.
Learn more about the Extended Spring Indices and the data products available.
USA-NPN also produces a suite of Accumulated Growing Degree Day map products.
What is behind these maps?
The Extended Spring Indices are mathematical models that predict the "start of spring" (timing of leaf out or bloom for species active in early spring) at a particular location (Schwartz 1997, Schwartz et al. 2006, Schwartz et al. 2013). These models were constructed using historical ground-baesd observations of the timing of first leaf and first bloom in a cloned lilac cultivar (S. x chinensis 'Red Rothomagensis') and two cloned honeysuckle cultivars (Lonicera tatarica 'Arnold Red' and L. korolkowii 'Zabelii'). These species were selected because they are among the first woody plants to leaf out and bloom in the springtime and are common across much of the country.
Primary inputs to the model are temperature and weather events, beginning January 1 of each year (Ault et al. 2015). Maps for the current year are generated using temperature products from NOAA National Centers for Environmental Prediction Real-Time Mesoscale Analysis. More information is provided in our Gridded Product Documentation.
To determine how the current spring compares to “normal”, we difference the day of year the leaf out or bloom was reached this year from the long-term average (1991-2020) day of year it was met. Long-term averages were calculated using PRISM Climate Data daily minimum/maximum temperature data (Oregon State University).
In 2022, we updated the period of comparison for our spring leaf out and bloom anomaly maps to the new climate normal of 1991-2020, following standards set by NOAA and the World Meteorological Organization. Climate Central offers more detail about how seasonal average temperatures have shifted from the prior to the current climate normal period.
To calculate how often we see a spring as early or late as the current spring, we compare the current year's Spring Index Anomaly value to the anomaly values from the previous decades. We determine how often a spring was at least this early (or late) by taking the number of years in the record divided by the count of years that were earlier (or later) than the current year.
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