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The dots rendered on these tiles for the U.S. show the average date on which the chances of freezing temperatures drop below 50 percent at weather stations across the United States, based on the 1991-2020 U.S. Climate Normals from NOAAs National Centers for Environmental Information (NCEI). In other words, past the date shown, temperatures have historically been more likely to stay above freezing than to fall below it again for the rest of the spring.
Places where this milestone is reached before the first day
of spring in mid-March appear in shades of purple, while places where it comes
after that are colored in shades of green. For most of the United States, the
odds of freezing air temperature remain above 50 percent until after the
official start of spring. As you’d expect, the farther north or higher in
elevation you go, the later in the season (darker greens) this day generally
arrives.
These tiles have a background image showing interpolated values for all locations in the Lower 48 states. (Interpolating
means estimating values where you don’t have direct observations, using
existing observations and physical relationships, such as the way temperature
changes with altitude.)
Gray squares are places where no date could be calculated.
Either that location is so chilly that the chance of freezing temperatures is
higher than 50 percent all spring (possibly even all year, as in parts of
Alaska and the highest peaks of the Western mountains), or it is so warm that the chance of freezing temperatures is below 50
percent all spring or all year.
The dots rendered on these tiles for the U.S. show the average date on which the chances of freezing temperatures drop below 50 percent at weather stations across the United States, based on the 1991-2020 U.S. Climate Normals from NOAAs National Centers for Environmental Information (NCEI). In other words, past the date shown, temperatures have historically been more likely to stay above freezing than to fall below it again for the rest of the spring.
Places where this milestone is reached before the first day
of spring in mid-March appear in shades of purple, while places where it comes
after that are colored in shades of green. For most of the United States, the
odds of freezing air temperature remain above 50 percent until after the
official start of spring. As you’d expect, the farther north or higher in
elevation you go, the later in the season (darker greens) this day generally
arrives.
These tiles have a background image showing interpolated values for all locations in the Lower 48 states. (Interpolating
means estimating values where you don’t have direct observations, using
existing observations and physical relationships, such as the way temperature
changes with altitude.)
Gray squares are places where no date could be calculated.
Either that location is so chilly that the chance of freezing temperatures is
higher than 50 percent all spring (possibly even all year, as in parts of
Alaska and the highest peaks of the Western mountains), or it is so warm that the chance of freezing temperatures is below 50
percent all spring or all year.