Any day now, really: Fall leaf colors to pop soon in Western Pa.

There wasn’t much peeping going on for the long-planned and sold-out Gateway Clipper fall leaf-peeping tour last weekend on the Allegheny River in Armstrong County.

Although the boat ride was spectacular in its own right, “it was disappointing we could not control Mother Nature,” said Chris Ziegler, president of the Armstrong County Tourism Bureau.

The Alle-Kiski Harley Owners Group also was poised last weekend to take in the fall leaf splendor, but postponed the ride to this weekend and possibly offer another ride the following week.

The Walk in Penn’s Woods, a statewide event, held locally Oct. 3 at the Otto and Magdalene Ackermann Nature Preserve in North Huntingdon, didn’t yield the expected hills painted in bright red and yellow.

Peak fall leaf colors in the Alle-Kiski Valley and Westmoreland County will likely occur this week into the weekend and possibly the following week if the cool nights persist, area experts say.

The long stretch of unseasonably warm temperatures earlier this month paused the process of green leaf pigment breaking down, giving way to the familiar fall hues of bright yellows, oranges, reds and russets of a variety of deciduous trees.

“We should be in our peak season now,” said Marc Abrams, professor of forest ecology and physiology at Penn State last week. “There are so many trees that are green, and ones that changed have done so in a dull way.”

The state Department of Conservation and Natural Resource’s (DCNR) weekly fall foliage reports said Armstrong, Butler and Westmoreland counties are approaching best color while Allegheny County is just starting to change.

Abrams predicts a mediocre fall, delayed by seven to 10 days for central and southern Pennsylvania.

Temperatures need to dip down to the low 40s and high 30s at night for the leaves to turn color. That is just starting to happen in the region this weekend, Abrams said. Sunday’s overnight low is expected to dip down to 40 degrees. Monday night should be even cooler at 38 degrees, according to recent forecasts.

The key ingredients for glorious fall color are clear sunny days with low but not freezing temperatures at night and dry but not drought conditions, said Abrams, who has studied the influences causing the color of fall leaves for 30 years.

Local experts concur with Abrams.

Brian Wolyniak, an urban and community forester with Penn State Extension in Allegheny County, said the fall foliage is late by a week or more. Pittsburgh and surrounding communities will run later than that because it’s always a few degrees warmer there.

Tony Quadro, forester for the Westmoreland County Conservation District, and Holly May, a DCNR service forester for Armstrong, Clarion and Jefferson counties, said fall foliage is running about a week late.

“The best color is always around my husband, Theo’s, birthday, which is today,” Pia van de Venne said on Tuesday. She is president of the Friends of Murrysville Parks. “Some colors are late and some are on time, like the red tupelo and Virginia creeper.”

Wolyniak admitted predicting the peak is a big question mark. “It’s hard to pinpoint when it will be that perfect day. It can vary from a mile or two up the road.”

But with night temperatures just starting to cool down, residents should get ready to peep and do it quickly.

Some of the ridges in Westmoreland County are peaking or getting close to peaking, said Rachael Mahony, a DCNR environmental education specialist in Forbes State Forest in the Laurel Highlands.

Fall foliage on Mt. Davis, the highest point in Pennsylvania at 3,213 feet, peaked last weekend; Laurel Mountain is peaking now, and Chestnut Ridge is running a week or so behind, Mahony said.

Generally, in Westmoreland County, Mahony expects colors to peak now until next week.

“It depends on where you are,” she said. “Some places have progressed and some places are still really green.”

Mahony lives in North Huntingdon. “I’m seeing a lot of the maples that are turning and a mix of some of the oak trees is changing ever so slightly.”

Once those colors come out, those leaves will drop quickly, she said. “Just get outside and explore your own backyard and visit a small park. It doesn’t have to be a fancy trip to the Laurel Highlands.”