Prove your humanity

Peak Colors are Coming to Southwestern Pennsylvania This Week

Leaves have already gone red, orange and yellow in much of the higher elevations of northern Pennsylvania. But the southwestern and central parts of the state should get their turn starting this weekend. Photo: Brook Ward via Flickr

The Allegheny Front has partnered with the online climate and weather almanac iSeeChange to help collect observations from people all across the country about what’s going on outside. And people have been noticing some strange things about the leaves on the trees where they live. Observers in Wisconsin and Michigan noticed leaves turning brown during the summer. And in Kansas, someone reported elm trees changing color in September.

So what’s going on with the leaves in Pennsylvania? It’s Rachael Mahony’s job to know.

LISTEN: Forecasting Peak Color Isn’t Just Anyone’s Guess. It’s Rachel Mahony’s.

Mahony is the environmental education specialist at Forbes State Forest in southwestern Pennsylvania’s Laurel Highlands. And each August, she makes a prediction about when leaves in her region will reach peak autumn splendor. To do this, she keeps a weather and nature journal to help her make an educated guess at the timing.

“Judging by the fact that we had kind of droughtlike conditions throughout most of the growing season, I could kind of presume that would delay the peak foliage,” she says.

The leaves have already gone red, orange and yellow in much of the higher elevations of northern Pennsylvania. But Mahony says this weekend through next week is when leaves will pop in the southwest. And according to the statewide fall color map compiled by the Department of Conservation and Natural Resources, that’s true for central Pennsylvania too. Mahony says it’s about a week later than most years.

“The black gums are usually the first trees that begin to turn, and those are already starting to drop leaves,” she says. “But a lot of the maples are still developing their color, and there’s still a good bit of green up top.”

Want to see when the colors are peaking on your favorite trail? Check out this statewide map compiled by Pennsylvania’s Department of Conservation and Natural Resources.

Deciduous trees need to go into a dormant state to survive cold winters. The shorter periods of daylight after the autumnal equinox are a signal for trees to get that process going. Production of chlorophyll—the green pigment that helps plants make food—slows down. And when this happens, other pigments called carotenoids are unmasked. They’re the same pigments that make carrots orange and do the same for leaves. Other pigments responsible for brilliant red hues are created by sugars in the leaves and are activated by sunny fall days and cool nights—the kind of weather we’ve been having lately.

But if you remember, just a few short weeks ago, temperatures were still in the 80s. And the dry winter and summer heat and drought stunned a lot of trees. Some dropped their leaves while they were still green, and others began to turn, but their leaves became splotchy. Mahony says she’s seen a bit more of that this year than is typical.

During drought years, the colors also tend to be a bit duller. But Mahony says from what she’s seen so far, leaf peeping still should be pretty sweet this year.

“I think that every fall is absolutely gorgeous in Pennsylvania. We’re very lucky.”


So what have you noticed about leaves, trees or the weather? Join the conversation at iSeeChange.org. Or download the app, and help us tell our region’s climate and weather stories.