Happy Equinox Day, Philly. Spring has a way of energizing humans and the atmosphere.

These are high times astronomically, meteorologically, and naturally, and not just because last year’s vernal equinox was followed by something that felt like a year-long national night.

At 5:37 a.m. Saturday, the sun’s direct light was directly above the Equator, or about 1,500 miles north of where it was beaming at the winter solstice in December, and the astronomical spring began in the Northern Hemisphere. So why did it feel more like astronomical winter?

Spring’s reputation notwithstanding, it is prone to be as extreme as it is colorful. It gives us that aesthetically underrated bud season, when the sunset light electrifies the tree branches. It follows with us those achingly promising first delicate greens, and that explosion of blossoms and flowers.

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It also gives us some of the most violent thunderstorms of the year; tornadoes; and yes, on occasion snowstorms.

As it does to most humans, spring has a way of energizing the atmosphere.

With the sun at September-like strength, winter is in retreat. But it’s not far away. Temperature contrasts that drive storms are quite dramatic this time of year, and a powerful storm that generates strong winds from the north can lure winter back in a hurry. For example:

Snow jobs:

The howlings:

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A day for all seasons:

Equality? Not quite. “Equinox” takes its name from the Latin root for “equal,” suggesting equal day and night. But the “equilux,” the even day-night split, actually occurred Tuesday. On Saturday, the day will be 9½ minutes longer than the night.

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Where are we? About 0.9898 AU (astronomical units) miles away from the sun, says Frank Maloney, astronomy professor at Villanova University. This is just slightly under the average annual distance of about 93 million miles.

Space-travel lag? It’s been a rough year, and we’ve all done a lot of traveling despite the lockdowns and restrictions. The earth has spun its merry way 574 million miles around the sun since the last vernal equinox, motoring at 67,000 mph.

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At least winter was short. It always is. The trip from winter to spring is just 140.8 million miles and takes only 88.98 days, says Maloney. A shortcut? No. The earth makes its closest approach to the sun in January, and it speeds up slightly. To adjust our calendars, February gets shorted by 2.25 days. In the Southern Hemisphere, winter is the longest season. It’s the first day of autumn down there.

At our latitude we are gaining about 2½ minutes a day of daylight daily, the most-rapid day-lengthening of the season. By comparison, the day-to-day differences are shortest at the solstice.

Light power: The sun rules. Even on a cloudy day, the sun’s illuminating power can be about 50 times that of indoor lighting; on a clear day, 450 times, according to University of Munich chronobiologist Till Roenneberg.

Light drugs: It’s not just the warmth, all this sunlight boosts serotonin levels, says Dr. Norman Rosenthal, the psychiatrist credited with identifying “seasonal affective disorder,” which addresses the symptoms associated with decreasing light in fall and winter. The increasing brightness gives us more energy. Thus all the “spring cleaning,” gardening, and house painting (in some of us, anyway).

Light sex: “There is a general increase in sexual activity and interest in the spring,” Rosenthal has said. “It’s clinically observable.” (We’ll leave it at that.)

The popular legend is true: You can indeed balance an egg on the day of the equinox. But if you don’t get around to trying it Saturday, no worries.

You can also do it on March 21, or you could have done it on Feb. 7, the Martian equinox, or on March 31, Aug. 20, or any other day for that matter.

The equinox is quite a special day, but not particularly for egg-balancing.