The U.S. Forest Service doesn’t outright call this spring, since some parts of the U.S. do not experience the traditional four seasons. But "greening" does indicate the transition to a warmer and leafier time around the country.
While the South is generally warmer than the North, the map shows some interesting microclimates. For example, warmer temperatures arrive sooner at lower elevations, while higher elevations green later in the year. Differences within regions can also be based on the type of foliage or crops: Deciduous forests warm much more quickly than Midwestern croplands, for example, which is why the fields of Iowa and Illinois appear blue.
There are some exceptions to greenup: Some extreme deserts never get green, while evergreen forests are green year-round. As a result, central Pennsylvania, the Adirondacks, New England, and mountain areas of the Pacific Northwest may show greening that is actually just the melting of heavy snow in conifer forests.
The Forest Service also created an extensive series of maps for different regions and cities around the country. You can see that cities tend to warm earlier due to the heat generated from buildings and asphalt. Here is Washington, D.C.:
New York and New Jersey:
A wider view of the east coast:
The city of Chicago:
The Lake Michigan area:
Minneapolis-St. Paul, Minn.:
Nebraska and Kansas:
Baton Rouge and New Orleans, La.:
The maps are fun to look at, but the forestry department emphasizes that this is among the most useful information it provides to people around the country, whether they are farming or just planting a garden.
More stories from Know More, Wonkblog's social media site: