(NECN: Danielle Niles) - The days get shorter, the nights cooler, and you can feel it in the air. The transition to fall has begun.
It's these simple day-to-day changes that kickstart another important process, one that many look forward to each autumn: the changing of the leaves.
"It's partly a function of how healthy the tree is during the growing season," said John O'Keefe, phenologist at the Harvard Forest in Petersham, Mass.. "A bunch of complex factors wind up contributing to what we actually perceive as the colors of the fall."
During the fall, all leaves gradually break down their chlorophyll, the green pigment that traps the energy of sunlight for photosynthesis. As this pigment breaks down, yellow starts to appear on the leaves.
It turns out, it's been there all along. It's just been masked by the pigment.
The beautiful red colors we see are a little bit different.
"It actually takes energy and sunlight to produce the anthocyanin," said O'Keefe. "It's not like an unmasking. It's actually an active chemical process that's required to make these red pigments."
In other words, the red pigment is a function of fall weather conditions. A healthy growing season helps, but cool nights and sunny days are key.
Energy will still make it to the leaves on cloudy days, but the result will be less vivid colors.
So what are the peak foliage times in New England? Primarily temperature dependent: Northern New England turns first and peaks from mid to late September.
Central New England follows, peaking in the beginning of October, with Southern New England after that, generally mid to late October.
About half the species in New England are able to make red pigments, but maples produce the brightest red and are one of the most common.
So whether a scenic drive, hike, walk or bike ride is your choice, there are plenty of ways to view New England's fall foliage.