When it comes to the timing of autumn color in different North American locations, the major factor is dwindling daylight, said Mike Pigott, senior meteorologist with AccuWeather in State College, Pennsylvania.

"It's mainly a product of shorter days and longer nights that begin to shut down photosynthesis," Pigott said. "At the northern latitudes you have noticeably shorter days in the fall versus the South. So that's the primary reason why, as a rule of thumb, the further south you are the later the leaves will change color."

This pattern creates a colorful wave that begins in the North and rolls like a tide southward through North America—though temperature differences at higher elevations mean some southern mountains keep schedules that are