Start of Spring

This indicator tracks the start of spring each year. The start of spring occurs on the date when enough heat has accumulated to initiate growth (leafing and flowering) in temperature-sensitive plants.
Date Range: 1900 - 2021
This indicator tracks the start of spring each year. The start of spring occurs on the date when enough heat has accumulated to initiate growth (leafing and flowering) in temperature-sensitive plants.

Start of spring is changing in the U.S.

On average, the start of spring has occured earlier in the contiguous United States since 1984. A trend toward earlier springs could have significant implications for agriculture, natural resource and hazard management, and recreation.
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The bars on the graph show the number of days by which the start of spring differs from the average start of spring during the last century.

About Start of Spring

This
indicator An observation or calculation that allows scientists, analysts, decision makers, and others to track environmental trends, understand key factors that influence the environment, and identify effects on ecosystems and society.
estimates the annual start of spring on the basis of when growth can begin for temperature-sensitive native and cultivated plants. It can be used to monitor, assess, and predict variations and trends in spring timing at the national scale.

The annual start of spring can be estimated for any location where daily minimum and maximum temperatures are recorded. The modeled values correlate well with observed leafing and flowering in a number of native and cultivated species, such as winter wheat, pear, and peach varieties.

These values are calculated from a numerical model that simulates the accumulation of heat needed to bring plants out of winter dormancy and into vegetative and reproductive growth. The model is based on:
  • Long-term observations of lilac and honeysuckle first-leaf and first-bloom, collected by citizen science volunteers at hundreds of sites across the contiguous United States
  • Daily minimum and maximum temperatures measured at weather stations

Why It's Important
  • The earlier arrival of the start of spring has been linked to recent warming trends in global climate.
  • This indicator can help decision makers understand and anticipate climate impacts on:
    • habitats and species
    • agricultural production
    • recreation
    • the management of natural hazards such as wildfires

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