The universe is calling winter kaput today as the sun’s rays cross Earth’s celestial equator, and day and night finish as equals.

March 20 is the spring equinox, the astronomical end of the darkest, coldest days of the year.

And while most of America set their clocks forward one hour March 12, the equinox is nature’s promise that earlier sunrises and later sunsets are imminent. The sun rises due east and sets due west on the equinox.

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"It means from now on, for the next six months, the days will be longer than the nights," said Sam Storch, a retired astronomy professor and member of the Astronomical Society of the Palm Beaches. "It is an opportunity to point out that the ancients were more in touch with how things changed in the sky than we are, and used the changes as benchmarks in their lives."

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In spring, the sickle-shaped head and torso of the constellation Leo appear in the eastern sky as belted Orion retires to the west, eventually disappearing in the sun’s glare by June’s summer solstice.

Storch said the rise of Leo was a signal for farmers to begin clearing fields for planting season.

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"Orion reminds us that winter has come to an end as we see it falling sadly into the twilight of the west," Storch said.

Astronomical seasons don’t correspond with meteorological seasons, which are grouped neatly by months to correspond with what are supposed to be the coldest or warmest days of the year. Meteorological winter ended March 1, while astronomical winter ends with the spring equinox.

Of course, Mother Nature is apt to flaunt rules. It brought some of the coldest air of the season to South Florida on Thursday after man’s calendar said winter was done. Temperatures dropped to 46 degrees at Palm Beach International Airport, a full 15 degrees below what’s average for mid-March.

Jacksonville and Gainesville set record low temperatures overnight Wednesday into Thursday morning, dipping to 28 and 25 degrees, respectively.

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In Washington, D.C. the late-season cold front caused widespread damage to the city’s renowned Japanese flowering cherry trees, which began budding early because of a mild winter.

According to a National Park Service statement, blossoms suffer damage at 27 degrees. The Capitol hit 24 degrees for several hours.

"Because the blossoms are so close to peak bloom and are exposed from the protection of the buds, they are particularly vulnerable to cold temperatures," the statement said.

Chris Fisher, a meteorologist with the National Weather Service in Miami, said the first week of astronomical spring should offer true spring-like weather for South Florida with near-normal temperatures in the high 70s and mostly sunny skies.

"We may see a weak cold front, but nothing like what we just saw," Fisher said. "Other than dropping dew points a little, there won’t be any real impact."

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