Signs of Spring: Astronomy, Seasons and Weather in March

The weather in March may be variable, but the first day of spring is entirely predictable.


| February/March 1993



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Look to the stars for the first signs of spring.


PHOTO: MOTHER EARTH NEWS

If you're dreaming of warmer weather, outdoor walks, and starting up your outdoor garden again, you're not alone. Most of us are anxiously waiting for the return of the robin--herald of spring. In fact, Americans get so hyped-up for the upcoming season that we have actually created a day for trying to predict when spring will arrive (a.k.a. Groundhog Day). Sure we still have the rest of winter to endure, but we can pursue the subject of spring's arrival--in the calendar, the weather, the living world, the heavens, and the holidays.

Seasons and Calendar

Technically, spring begins in the Northern Hemisphere when the sun moves northward enough to pass overhead as seen from Earth's equator. We call this point-and the sun's reaching of it-the spring, or vernal equinox. (Equinox means "equal night," referring to the fact that day and night are equal in length at this time of year.) It is also at spring equinox (and autumn equinox) that people all over the world can see the sun rise exactly due east and set exactly due west.

The first day of spring always falls on one of two days: March 20 or 21. This year, 0you can celebrate on March 20 at 9:42 A.m., Eastern Standard Time. Will that be the moment when we feel warmer, see a burst of green around us, smell flowers leaping into bloom? Doubtful. As Henry Van Dyke put it in Fisherman's Luck, "The first day of spring is one thing, and the first spring day is another. The difference between them is sometimes as great as a month." Also, a first spring day is generally followed by a few cold snaps and a return to winter, a kind of reversed Indian Summer. On March 7, 1855, Henry David Thoreau noted in his journal: "The first pleasant days of spring come out like a squirrel and go in again."

In Like a Lion, Out Like a Lamb

Most of us have learned to expect nothing from March except the unexpected. We should be well aware that weather in this month is a throw of the dice, a total gamble. In fact, March is appropriately named for the Roman war god, Mars, since no other month brings such a war between warm and cold, between winter's refusal to leave and spring's insistence on coming. If March 1 is a peaceful, almost balmy day, you can be relatively sure that March 31 will be stormy and cold.

Most people tend to recall the spectacular; in weather, this means storms. The frequency of tornadoes takes a leap up in March, most of them occurring well south in the Gulf states. Some parts of the country may experience violent thunderstorms, followed by blizzards or ice storms. I recall that March of 1989 in our town was a month of flu, 4" of sleet on the ground, tornado watches, and one of the most spectacular Northern Lights displays of our lives-all these happenings violent or eerie, unsettling and potent, and sometimes occuring with great beauty, as in the case of the Northern Lights. March has been the month of the most devastating tornado and the most famous blizzard ever (see "Almanac Timetable").

But then, just when you can't stand it anymore, when you are sick of bulky sweaters and sore throats, March brings us closer to the equinox-the sun gets higher and the days lengthen more rapidly. December, January, and February are the true winter months; March makes a stride towards what most of us think is the most delicious of outdoor weather. The proof is in March's effects on plants and animals.

The Living World

Although the length of day plays a direct role in starting changes in plants and migrations in animals, much also depends on temperature. Spring peepers don't begin their calling until the average temperature rises above about 50°F, but the most famous animal indicator of spring moves north in both the eastern and western United States, almost precisely with the 37°F line. That is the air temperature at which the ground is generally thawed enough to permit earthworms to come to the surface-where they will soon become the meal of the arriving robin.





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