WOODSTOCK, Vt. — Jon Bouton does his leaf-peeping from his car, traveling Vermont’s bumpy back roads in a 2001 Geo Prizm.

When the sugar maples, ash and poplars begin to show their colors, the Windsor County forester sends e-mails to the state tourism office, describing where the colors are brightest and what roads to drive to see them. His counterparts in Vermont’s other 13 counties do the same twice a week, their reports eventually combined into an online “foliage forecast.”

Bouton, 59, is part of a small army of foresters, park rangers, volunteers and attraction operators in foliage-rich states whose observations point the way.

Jeanne Curran, a spokeswoman for Maine Department of Conservation, said the department relies on park rangers for leaf reports, adding that “technology allows us to do quicker, more accurate foliage reporting, which is absolutely essential for our fall visitors.”

Regional forecasts also come from volunteer spotters who deliver reports about what roads to drive, which kinds of trees are turning and when the peak periods of color will be.

Fall foliage is a multimillion-dollar business for tour operators, inns, restaurants and attractions that cash in on the rush of camera-toting visitors. Nowhere is it more vibrant than in New England, where a predominance of maple trees produces a dazzling display of red, yellows, oranges and browns and everything in between.

In Vermont alone, visitors spend $374 million a year in the September-to-November season.

Typically, the foliage season runs from the end of September to mid-October, when chlorophyll in the leaves breaks down because days are getting shorter and nights colder.

Forecasting the colors is not new, but the Internet has boosted its immediacy and given leaf lovers new tools for going where the color is. Visitors can get foliage forecasts from state-run telephone hot lines that advise where to go and online — in words, maps and photos.

New Hampshire, which gets observations from three dozen designated “leaf peepers” from chambers of commerce and lodging properties, offers foliage text alerts for those who want them, as does Massachusetts.

Massachusetts uses park rangers who e-mail their reports twice a week.

“It’s not based on predictions, it’s based on actual observations,” said Betsy Wall, executive director of the Massachusetts Office of Travel and Tourism.

As for this year’s foliage forecast, experts say the summer’s hot, dry weather could make for more muted colors, an earlier start, both — or neither.

University of Vermont plant biologist Abby van den Berg, who has done research on leaf colors, said some data suggest a small amount of physiological stress can result in more brilliant colors.

“The real bottom line is that there’s no great way to predict these things,” she said. “It’s pretty much impossible, especially over a large scale.”

Online: Maine foliage tracker: www.mainefoliage.com; New Hampshire foliage tracker: http:///foliage.visitnh.gov; Vermont foliage forecaster: www.vermontvacation.com/fallfoliage2010/fallfoliage2010.asp