For 30 years, Marc D. Abrams has meditated on the mysteries of the woodlands and the mystical magic of autumn. So he was asked where he would go for that maximum feasible foliage experience. His answer was as disappointing as it was unsurprising.

"That is a tough one," he said, "because I have seen great colors throughout New England, upstate New York . . . and down the Appalachian Mountains to Virginia and North Carolina." I was holding out hope for that miraculous revelation, an undiscovered jewel, but I guess a few million of us would give roughly the same answer. I would, however, add the colors that Abrams, a Pennsylvania State University professor of forest ecology, has seen in his own state, not for naught called Penn's Woods. My autumn canvas would include the foliage I have seen even in New Jersey, especially the northwest, and in the special wooded areas in and around Philadelphia, including the Wissahickon Valley.

THREE BASIC PIGMENTS

Best spots for fall foliage

What's behind the show? The variations of nature's palettes are almost endless, but autumn colors are driven by three basic pigments: carotenoids (the yellows and oranges of corn and pumpkins), anthocyanins (think cranberries and apples) and basic green chlorophyll.

Responding to autumn's light cues, chlorophyll in deciduous trees recedes and yields to yellows and oranges. Then, as food-bearing veins at the leaf base shut off, the stranded sugars manufacture the show-stealing anthocyanins that turn leaves aflame.

It is impossible to predict just how brilliant an autumn will be in any given woods, or any given species, for that matter. But Abrams says the best colors depend on favorable weather during the growing season -- that is, with adequate but not excessive rain. Those requirements generally have been met in the East, which has been spared the leaf-shriveling drought conditions of the West.

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WHEN TO GO

In far northern New England, the peak typically comes in late September. By contrast, color in the lower elevations of the Blue Ridge might not get underway until mid-October and peak in November.

The seasons do vary, and a foliage trip sometimes is a game-day decision. But a government-run site developed by Xiaoyang Zhang at South Dakota State University might be a big help. Using satellite data, it monitors conditions every three days and predicts what will happen 10 days out in six color-intensity categories.

Considerable research is being devoted to whether worldwide warming is pushing back the season. Earth's temperatures are running about 1.5 degrees warmer than in the 20th century, according to federal data, and the warming in the Northeast has been about the same.

One of the most detailed records we've seen was started by 87-year-old Nancy Aldrich, daughter of the founder of Polly's Pancakes, in Sugar Hill, New Hampshire, a famed tourist destination. Since 1975, Polly's has kept track of the dates of onset, peak and season finales. Onsets and peaks haven't changed much on her chart, but the season has been hanging on about five days longer up her way, until Oct. 10.

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BEST VIEWING CONDITIONS

Just as important as when you decide to go is when you decide to look. Those splendidly sunny autumn middays are for walking in the cathedrals of the woods as the sunlight turns the leaves to stained glass. For panoramas, slate skies make for better backgrounds, and not too many natural phenomena can match the light-and-shadow interplay on hillsides as rapidly moving clouds race across the sun.

My favorite time is around sunset, when a hidden sun might slip beneath a cloud in just the right angle to electrify the leaves, barks and treetops. Stay around for twilight, when the subtlety of leaf color is exploited by the remnants of daylight.

And if you're fortunate to be somewhere on a clear night with a full moon, catch the silvery light on the colored leaves. The moon will be full this week and again in late October.

What I've learned to appreciate most about autumn are all the things I notice almost incidentally, what the writer-philosopher Robert Pirsig called "corner-of-your-eye" experiences. At Moosehead Lake, in the wilds of Maine, I was driving down a steep mountain road, hoping to live through the experience, when I caught a glimpse of foliage the like of which I had never seen. I had a similar instant on the Blue Ridge in North Carolina, as the car emerged from a low cloud.

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I've had other moments that were close, and I've never known an autumn to disappoint. Enjoy what comes your way, but above all, relax, and be grateful.

LEAF PEEPERS' GUIDES

A government-run site monitors conditions nationwide every three days and posts 10-day forecasts in six color-intensity categories: nwsdy.li/foliage.

A private site offers weekly forecasts in seven color categories: smokymountains.com/fall-foliage-map.