Peak fall foliage colors are expected around Oct. 11, according to DCNR District Forester Cecile Stelter.

The combination of “warm sunny days and cooler nights” produce “ideal conditions that set us up for good fall foliage,” she said. “(We) anticipate that is going to continue.”

Color is starting to pop up in places and will peak in a couple weeks, starting to fade around Oct. 20.

That’s “pretty typical timing for this area,” Stelter said. “From what we’re seeing, we’re going to see some really bright spots.”

Times Observer photo by Josh Cotton Some of the trees along the Allegheny River are starting to turn color. Peak fall foliage time is projected for around Oct. 11.

According to the Department of Conservation and Natural Resources, Pennsylvania has a “longer and more varied fall foliage season than any other state in the nation — or anywhere in the world.”

Only three regions in the world support full autumn color — eastern North American, the British Isles and parts of western Europe and northeastern China and northern Japan. Forests in other areas are either tropical or dominated by conifers, per DCNR. Stelter said Warren County is also in a unique spot in the state here because of a “diversity of tree species” — more than 120 in total — that “brings added color and added beauty to it.”

DCNR also highlights Pennsylvania’s location — between 40∂ and 42∂ North latitude — and its varied topography from sea level to over 3,000 feet as additional contributing factors. Stelter said if someone misses peak foliage in one place it only takes a 1.5- or two- hour drive to catch it in the next area.

“(You) can really watch it progress across the state,” Stelter said.

According to farmersalmanac.com leaves will peak across the state between Oct. 5 and 21, but there’s a big difference between southern Pennsylvania and northwest Pennsylvania. According to an animated map on the Old Farmer’s Almanac website, almanac.com, leaves fall colors are expected to begin to peak in Warren County in about two weeks. By Oct. 28, the late peak season is expected to arrive. By the first week of November, leaves are expected to be past peak. The map is based on previous year’s records and expected precipitation and temperatures.

According to AccuWeather, the peak foliage season will hit Warren in early to mid-October. The company predicts the northeastern states in general will have some of the best displays of fall color anywhere in the country this year. Late spring to mid-summer wet weather and dry sunny days with cool nights in September encourage more vibrant fall leaf displays, according to AccuWeather. Leaf colors are dependent on three sugar-based chemicals, according to the U.S. Forest Service: the chlorophyll, carotenoids and anthocyanin. Chlorophyll gives leaves their basic green color. Carotenoids give plants their yellow, orange and brown hues. Anthocyanin provides red, purple and blue hues.

“Both chlorophyll and carotenoids are present in the chloroplasts of leaf cells throughout the growing season. Most anthocyanins are produced in the autumn, in response to bright light and excess plant sugars within leaf cells,” according to the USF website. “During the growing season, chlorophyll is continually being produced and broken down and leaves appear green. As night length increases in the autumn, chlorophyll production slows down and then stops and eventually all the chlorophyll is destroyed. The carotenoids and anthocyanin that are present in the leaf are then unmasked and show their colors.”