Mar
04
2005

There is probably no day greeted with greater joy and anticipation than the first day of spring -- especially after a Minnesota winter! Sometimes, the only thing that gets us through February is knowing that better days are on the way. But when, exactly, does spring get here?

TV weathermen will tell you that spring starts on the vernal equinox -- the day when the number of hours of daylight are equal to the number of hours of night. (In 2005, this falls on March 20.) The problem is, the weathermen are wrong.

Seasons are not astronomical phenomena; they are climatological phenomena. Or, to put it in English: seasons aren't about the sun in the sky; they're about the weather on Earth. They are defined by temperature. Winter is the coldest part of the year, summer the warmest, and spring and fall the periods in-between. On average, the coldest part of the year runs from December 4 through March 4. Which makes Saturday, March 5, the first day of spring!

Now, the problem is, this date is just an average. In any given year, there will almost certainly be nicer days before it and lousier days after it. Which is probably what led the weathermen to go with the equinox. It's very predictable -- down to the minute -- and there's no arguing: the days before it are shorter, the days after it are longer. (It's also three weeks later, which means the chance of nasty weather after your "first day of spring" is diminished.)

But daylight isn't the issue. Temperature is what counts. Besides, if you make the equinox the first day of spring, then the first day of summer will be the solstice -- the longest day of the year, June 21. And, as all good Scandanavians know, the longest day of the year isn't the first summer's day; it's MID-summer's day!

The first day of each season, according to average temperature:

  • Spring: March 5
  • Summer: June 4
  • Fall: September 4
  • Winter: December 4

(To learn more about how the Sun and Earth create our seasons, visit the Weather section of the Experiment Gallery on level 3.)

Your Comments, Thoughts, Questions, Ideas

Anonymous's picture
Anonymous says:

But why does an exact MINUTE start springtime? Is is about the positioning of the earth?

posted on Tue, 03/21/2006 - 8:36pm
Bart's picture
Bart says:

Thanks for the insight Gene. And what is your degree in?
It seems to me that you were getting somewhere recognizing MID-summers day. The seasons should be treated like the time zones. The demarcation for the hours from GMT is 15 deg per hour; putting the 6th hour west at about 90deg W longitude, pretty close to St. Paul. However, the Time Zone covers 82.5 deg W to 97.5 deg W "more or less." With this in mind, MID-spring would be March 20th but, the season of spring would run from about Feb 5 to May 4. The Summer Months would be May 5 to Aug 4. Fall Aug 5 to Nov 4 and finally winter from Nov 5 to Feb 4.

Being a Minnesota boy myself, this sounds pert near right.

posted on Sun, 03/13/2005 - 11:59pm
Anonymous's picture
Anonymous says:

As suggested by some other respondents, it seems to me that different latitudes and cultures need to be considered when defining seasons. Seasons clearly have different lengths and mean different things in Minnesota and Florida, and such differences become even more pronounced the closer one gets to the poles or equator. In the tropics, for example, climatic seasons are marked primarily by changes in precipitation (wet seasons and dry seasons), not by temperature (which are generally fairly warm), and the sun's rays are most direct twice each year, not simply on the "summer" solstice. Seasons are also cultural inventions, tied to varying work and agricultural calendars, such as summer in the U.S. traditionally being the time when schools are closed between Memorial Day and Labor Day. To use the equinoxes and solstices as precise dividers between seasons only makes sense from the perspective of someone standing on the sun. Here on earth, however, there are far too many local variables to insist on some official, "scientific" starting moment for each season.

posted on Fri, 03/24/2006 - 11:07am
Gene's picture
Gene says:

This cartoon seems to sum up the discussion very nicely. ;-)

posted on Sun, 03/26/2006 - 10:30pm
Gene's picture
Gene says:

The exact minute is the vernal equinox -- the moment that the Sun is directly above the Equator. The Earth is tilted on its axis, and as it circles around the Sun different points on Earth are closest to the Sun on different days:

  • On the summer solstice -- Midsummer's Day, usually June 20 or 21 -- the Sun is directly over the Tropic of Cancer -- an imaginary line that circles the globe. (It passes just south of Florida and just north of Cuba, cuts through central Mexico, goes just north of Hawaii, and then on through southern Asia and northern Africa.)
  • On the winter solstice, six months later, the Sun is directly above the Tropic of Capricorn -- another imaginary line, this one passing through South America, southern Africa, and right across Australia.
  • And in between we have the equinoxes, when the Sun crosses the Equator.

This movement of the Sun in the sky is very regular and predictable, and can be used to split the astronomical year into four very precise quarters, down to the minute. But, as I argue in other posts, this is not directly related to climate and temperature here on Earth, and thus makes a poor choice as a start of spring, as that term is commonly understood.

posted on Wed, 03/22/2006 - 10:24am
Gene's picture
Gene says:

I have a BA in BS. Thanks for asking! ;-)

What you describe are known as cross-quarter days. (Scroll down to "Dividing the year.") These are the dates that fall mid-way between an equinox and a solstice. Ancient agricultural cultures celebrated these days as signposts in the cycle of the year. Those celebration live on in such holidays as Groundhog's Day, May Day, and Halloween.

But February 4 as the first day of Spring? That feels a tad early. Especially for Minnesota!

posted on Wed, 03/22/2006 - 2:20pm
Kalia's picture
Kalia says:

I don't think weathermen(women) know what they're talking about sometimes. I don't blame them though, Mother Earth just have its own way of doing things. I'm just glad that "Spring" is here, even though there'are still some snow on the ground. But the days are getting longer, which means I can stay out longer. I'm just glad that spring is here... Happy Vernal Equnox! (even though it was yesterday).
kalia

posted on Mon, 03/21/2005 - 5:17pm
Anonymous's picture
Anonymous says:

What hour and minute will it be the first day of spring in the Ny time?

posted on Thu, 02/09/2006 - 4:45pm
Gene's picture
Gene says:

As we said above, "spring" is a matter of definition.

The day that the coldest part of the year ends: as noted, that's March 5.

The day that the darkest part of the year ends: February 4.

The moment the Sun is directly above the equator: March 20 at 1:26 pm EST (that 12:26 in Minnesota).

The first warm, spring-like day: that's anybody's guess!

posted on Thu, 02/09/2006 - 6:34pm
What time??'s picture
What time?? says:

so does that mean spring starts on March 5th at midnight?\r\n\r\nOr does spring start a certain time during the day?

posted on Mon, 03/06/2006 - 8:03am
Gene's picture
Gene says:

The only definition of spring that is tied to a specific minute is the vernal equinox definition (which, as noted above, falls on March 20 this year). Though I suppose the cross-quarter definition (February 4) would have it begin at sunrise.

As for the warmest-quarter definition (with spring beginning on March 5), then yes, midnight at the beginning of that day would work. (Though here in Michigan, we are having a most un-springlike snowfall.)

posted on Mon, 03/06/2006 - 9:24am
RussD's picture
RussD says:

There is no burning controversy here. And I dont think too many people are surprised when northern hemisphere summer officially starts in June or when winter officially starts in December when it is already cold and dark outside. What is important is consistency. Consistency is a GOOD thing in science so it is perfectly reasonable to pick an astronomical date that can be reliably predicted to define the seasons. The problem with tying it to temperature is the local averages will change over time and meaning of spring or summer will change over time.

What you are proposing is to qualify spring by choosing something like "vernal spring", "cross-quarter spring", "average temperature spring" or something like that. Sounds dreadful. Ever look up the definition of twilight? There are three distinct ways to describe it.

Vernal Equinox is on March 20, at 1:26 PM Minnesota Time...Yay spring.

RussD
(Meteorologist and Astronomer)

posted on Mon, 03/06/2006 - 6:31pm
Gene's picture
Gene says:

Consistency is a good thing in science. In real life, it's boring, and generally unobtainable.

You're right--there is no controversy. "Spring" is the return of warm weather, and has been defined in America as "March, April and May" for quite a long time. Indeed, it is still so in our meteorological records. Only in recent decades has there been this imposition of the equinox -- an attempt to standardize something which by its very nature is amorphous. Reasonable people laugh and ignore it.

Tomorrow in Michigan, it is supposed to be 50 degrees and sunny. If that is not spring, then the word has no meaning.

posted on Tue, 03/07/2006 - 12:11pm
Anonymous's picture
Anonymous says:

Recognizing cross quarter days are not a new idea. The ancient Irish did so; their sacred and holy days corresponded not only the the equinoxes and the solstices, but the cross quarter agricultural of Imblc (Feb. 2: when the days were getting noticably longer and the grazing animals returned to the hills), Beltane (May 1: maypoles and planting), Lammas (Aug. 1-3: the first harvest and the sacrifice of the harvest deities) and Samhain (Oct 31 & Nov. 1; aka: Halloween, the final harvest, ancestor holiday and animal butchering).

These same holidays are celebrated by neo-Pagans who celebrate this cycle as well as the lunar cycle as part of their religious practice.

posted on Sat, 03/11/2006 - 3:50pm
Anonymous's picture
Anonymous says:

When the Sun crosses the celestial equator going northward at the point called the vernal equinox spring officially begins. Vernal comes from the word for green. The green equinox marks the beginning of spring. Equinox comes from the word for equal: subsequently the day of equinox has equal amounts of daylight and darkness. -Tom -Amateur Astronomer

posted on Wed, 03/15/2006 - 5:46pm
Gene's picture
Gene says:

One small error: there is nothing "official" about the vernal equinox. There is no "office of the seasons." As noted in the link embedded in the original post, no scientific office or bureau has declared a "first day of spring." The closest we have are various weather bureaus, which use March 1 as the beginning of their spring records.

The concern, if it is one, is that March-April-May is not precisely one-quarter of the year. This bugs some people. And spring is a weather-based phenomenon, and weather is very unpredictable (as the big snowfall in Minnesota last weekend demonstrated!) This also makes declaring spring a hazardous business.

Astronomers have long used equinoxes and solstices to divide the year into four equal quarters, right down to the minute. The sky has no late-season storms, and is very reliable. One of those events occurs during spring, and has seepend into popular culture.

But, as noted, it is not meaningful to those of us who live on the surface of the Earth. Spring is the return of warm weather, and that happens -- haltingly, failingly, in all its glorious imprecision -- the first week of March.

Happy spring!

posted on Wed, 03/15/2006 - 6:40pm
Anonymous's picture
Anonymous says:

No there is no office of the seasons, but there IS a cause and effect of the seasons. After the equinox in March it DOES get warmer, EVERY year. And as the Earth travels around the sun, the source of the forcing is purely astronomical. Spring does follow winter and summer is not far behind.

Winter storms like the one in Minnesota this week are spring storms by your reckoning. Or is it suddenly winter again?

It is really funny how you have jumped on this bandwagon for some reason. I dont think you are gong to be changing any minds very fast Gene.

posted on Thu, 03/16/2006 - 10:20am
Gene's picture
Gene says:

As the link embedded in the original post notes:

...Kevin Trenberth, a climate researcher at the University of Illinois in Urbana [says] "Although the sun-earth geometry is clearly the origin of the seasons on earth, it has nothing directly to do with temperature or weather."

The weather gets warmer every year after late January. The key is when we leave the coldest part of the year. On average, that happens the first week of March.

You may call the recent snows a spring storm if you wish. Or, more accurately, you could say that spring is late this year.

(As noted above, on March 10 it was 65 and sunny here in Michigan. I suppose you would consider that "winter.")

I have jumped on no bandwagon; I am defending the traditional and sensible definition of spring. The fact that the TV and radio announcers must remind us every year of equinox-based trivia indicates that the culture at large isn't buying it.

You can say "March 21" all you want, but everybody knows the weather had already changed.

posted on Thu, 03/16/2006 - 3:22pm
Anonymous's picture
Anonymous says:

at what time does spring start at???????

posted on Mon, 03/20/2006 - 10:09am
Liza's picture
Liza says:

If you're asking when the Vernal Equinox is, it's today, March 20th, at 12:26 pm.

posted on Mon, 03/20/2006 - 10:29am
Eve's picture
Eve says:

hee hee :) its 14:25pm here right now.

I live in the southern hemisphere (South Africa) - and our Spring day is coming up on 01 Sept! We're very excited coz this is going to be a wonderfully hot summer :)

It snowed (very lightly) for the first time in 8years, here in Johannesburg just last wednesday :)

posted on Mon, 08/07/2006 - 7:25am
Ani's picture
Ani says:

i think that spring is the best season of the year. And in spring people fall in love usual than in other seasons.With best wishes.

posted on Wed, 02/28/2007 - 11:35am
Anonymous's picture
Anonymous says:

bring on spring!

posted on Tue, 03/20/2007 - 6:54pm

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