Signs of Spring: Astronomy, Seasons and Weather in March

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PHOTO: MOTHER EARTH NEWS
Look to the stars for the first signs of spring.

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.

In reality, robins aren’t entirely absent throughout the
United States during winter. The catch is that robins who
live quite far north in summer may not go as far south. For
instance, Canadian robins may be seen in winter in the
mid-Atlantic states. Nevertheless, their numerous arrival
in March is a noticeable event. Incidentally, it’s male
robins who show up first; females arrive weeks later,
setting the males to singing, as mating and territory
rituals begin.

In March, the southernmost United States sees oats and corn
and other spring crops coming out of the ground. Spring
wheat is planted in the southern part of the wheat belt.
Fruit trees blossom across much of the South. But in the
northern states, only a few hard plants are sprouting, and
a few of the earliest flowers and flowering bushes are
putting forth their blossoms.

Astronomy

Regardless of weather, February and March evenings bring
forth the same familiar constellations in the sky each
year. The brightest star, Sirius, twinkles mostly
blue-white in the South. Over in the Northeast, the Big
Dipper stands on its handle like a giant question mark in
the early evening. One sure sign of spring coming is Leo
the Lion, with his heart-star Regulus, rising in the East
after nightfall. But in February-March 1993, the
constellations are upstaged by four bright evening planets,
two of which-Mercury and Venus-are at their highest due to
spring’s celestial geometry.

Mercury never sets too long after the sun. But for about a
week before and week after February 21 this year, you may
spot it as a fairly bright point of light low in the West,
roughly 45 minutes after sunset.

Venus is now so brilliant that it may be mistaken for an
airplane or reported as a UFO; you may be able to find it,
about halfway up the Southwest sky, even before sunset. The
most spectacular sky sight for the whole United States in
the first five months of 1993 may be the very close pairing
of Venus and the crescent Moon at nightfall on February 24
(see diagram on page 19). That night, Venus is at its
greatest brilliancy and may actually surpass the thin
Moon’s brightness.

As March begins, Venus is setting more than three hours
after the sun, but by month’s end it will sink below the
horizon only a few minutes after the sun does. This is
Venus’ most dramatic exit from the evening sky in eight
years and offers us our best chance to see several amazing
sights: the long skinny crescent phase of Venus in steadily
held binoculars; Venus as

“Evening Star” one night and “Morning Star” the next
morning (see diagram).

Our other evening planets are Mars and Jupiter, and both
are now excellent to turn your telescope towards, if you
have one. (See accompanying diagrams to help find them.)

Special Days

-In January or early February, you may be so desperate for
spring that you are ready to believe a colorful piece of
weather lore which, in fact, has no real basis. Welcome to
Groundhog Day.

February 2 is about halfway between the winter solstice and
spring equinox. Thus it became one of the year’s four
“cross-quarter days,” halfway between the starts of the
seasons. And this seemed an appropriate time to try and
judge what the second half of winter would be like: “If
candlemas be fair and bright/Winter will have another
flight/But if it be dark with clouds and rain/Winter is
gone, and will not come again.” Why would a fair day
suggest that the rest of winter would be cold? Fair days in
winter do tend to be somewhat colder, but the fact is that
February 2 fair and cold tells nothing of what the days
ahead will be like.

The groundhog theme probably came from the idea of
hibernating animals coming out, finding the air too cold,
and going back to wait out more winter. Whatever the case,
tradition arose from Great Britain and Germany, where it
was the bear or badger that came out. In the eastern United
States-the groundhog (woodchuck) has been substituted. And
one particular groundhog in Pennsylvania has become the
media’s star performer in this supposed predicting act.