Fall foliage questions

There is no single date. Color begins in September in Colorado’s high country and the far north, peaks across much of New England, the Great Lakes and the Appalachians during October, and finishes in early to mid-November on Long Island, in New York City and at lower elevations in the South.

Among the states we cover, Colorado: aspens above 9,000 feet start in early September. Northern Maine, the Adirondacks and Vermont follow in the last week of September, along with northwestern Minnesota.

Briefly in any one spot. Minnesota’s DNR says peak usually lasts about a week in each area. A region as a whole stays colorful longer because slopes, valleys and species turn at different times.

Weather. The Forest Service says warm, sunny days and cool but not freezing nights give the most brilliant reds. A severe summer drought can delay color by a few weeks, and a warm fall dulls it.

Yellow and orange come from carotenoids, which are in the leaf all summer. Red and purple come from anthocyanins, which some species make in autumn from sugar trapped in the leaf. Red maple turns scarlet; aspen and hickory turn gold.

Yes, in the right places. New York’s tourism office lists early to mid-November for Long Island and New York City, and early November for the Hudson Valley and Finger Lakes. The lower slopes of the Smokies and parts of Georgia are also in color in early November.

From the state agencies. Pennsylvania’s DCNR publishes a report every Thursday in season; Minnesota updates its Fall Color Finder every Thursday through October; Maine, New York and Virginia issue weekly reports. Links are in our peak times table.

Locally, yes. In the Great Smoky Mountains color develops above 4,000 feet in early to mid-October and below that from mid-October to early November. Driving uphill or downhill is the quickest way to find color.

They are the typical windows agencies publish, translated into calendar dates with a fixed rule. They tell you the right week in a normal year, not the exact day this year.