Fall arrived in Philly at 2:50 a.m. Saturday. Here are some observations on the new season.

The days are ending just a shade more abruptly these days, with the sun tucking into that mystical envelope of the horizon a little faster than usual. That’s what happens around the equinox, which occurred at 2:50 a.m. Saturday, the instant that the sun beamed its direct light on the equator and the astronomical fall began, ruling until winter arrives on Dec. 21.

But, one season at a time. Locally, the fall of 2023 is looking decent for foliage color, and while we may be leaking daylight, next week should be a harvest for moon connoisseurs. Here are a few observations to mark the season, including the fact that it once marked the new year for the French. But not for long.

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Fall foliage experts say the key to color intensity would be a sequence of sunny days and cool nights leading up to the days when the green chlorophyll pigments retreat and allow the more-dramatic yellows, reds, oranges, and cinnamon browns to take over the leaves. Assuming they’re right, this has been a real good eight days, with plenty of sun and coolish nights. Following an expected weekend storm, the forecasts are calling for the return of the sunny-day, cool-night regime for several days.

Starting next Friday, Pennsylvania will begin publishing its weekly foliage reports, indicating that the show is underway in the Keystone State. The New Jersey Forest Service is providing updates on Facebook.

» READ MORE: The best places to see fall foliage in the Philly region

Areas to our north have been seeing them, but we’ve been striking out on the northern lights that have been electrified by solar storms. But Rob Steenburgh, the acting lead of the Space Weather Forecast Office, is convinced that our night will come.

“There is still hope!” he said this week. “In fact, the situation is improving two ways: The solar cycle continues to climb towards maximum and the nights are getting longer,” meaning longer windows of visibility. Be aware, however, that solar storms aren’t easily predictable, and the aurora is prone to occur without much notice. You can track the aurora forecasts at the Space Weather Prediction Center site.

As Steenburgh suggested, those daily corridors of light continue to shrink. On Friday, for the first time since March 11 — the eve of the spring clock change — the sun will set before 7 p.m. This is the year’s peak daylight-loss period. The time from sunrise to sunset will shrink by two minutes and 37 seconds on Friday, compared with Thursday. The daily rate of loss will decrease ever so gradually, eventually dropping to zero around the solstice, when the sun will set at ... you probably don’t want to think about that yet.

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The equinox, despite the Latin root, doesn’t mark the exact date for equal day and equal night at Philadelphia’s latitude. The closest we come will be Wednesday, when the time between sunrise and sunset will be 11 hours, 59 minutes, and 55 seconds.

Nothing against us, but the sun will be making quite the quick exit these days. It will be setting due west at the equinox, dropping straight down, as opposed to setting at angles to the north or south as it does during the solstices. So, it will disappear faster. If you want to savor this, don’t blink. It takes about two minutes and 45 seconds for the sun to vanish once it appears to make contact with the horizon at the equinox, about 30 seconds faster than at the solstice, according to EarthSky.

If you’re up for it, the sun also rises faster in the morning since it pops straight up. Might be a good time to wind that sundial.

Come next week, the full moon will be more than a pale substitute for the setting sun. It will be the last of a sequence of “super moons,” in which the full moon is making a close approach to Earth and will be 30% brighter than it is when it’s at its farthest points. The instant of fullness occurs at 5:30 a.m. Sept. 30, but it will be at a robust 99.5% fullness when it rises at 7:05 p.m. on the 29th. Incidentally, it will still be at 99% at moonrise — 7:31 p.m. — on the 30th, which isn’t exactly lights out. The next super moon will occur on Feb. 9.

» READ MORE: What to know about 'super' and 'blue' moons

Moonlight will flood the skies earlier next week than it does normally during the nights preceding and succeeding fullness. Usually, the moon comes up about an hour later each night. However, from Tuesday through Oct. 1, it will rise less than a half-hour later each night, all the more time to savor moon shadows before bed.

Since in the days before electricity, it gave them some extra light with which to work into the evening during the harvest season, farmers called the full moon nearest the equinox the “harvest moon.”

Once upon a not-very-long time, Sept. 22 was new year’s day in France. The “French Republican Calendar,” established after the French Revolution, was part of a campaign to eradicate the monarchal and religious past. The months were named for natural concepts and the dating system reordered. What was Sept. 22 to Oct. 21 on the Gregorian calendar became Vendemaire, the month of the grape harvest, in 1793. The first day marked both the new year and the birth of the French Republic. As with so many concepts associated with the revolution, the calendar’s re-making was contentious. One of the principal authors went to the guillotine; the other reportedly avoided that fate by taking his own life, according to the World History Encyclopedia. Napoleon ditched the calendar in 1806.