Leaf-peepers looking for the richest reds and the warmest golden hues will do good spending their time right here in northwestern Pennsylvania this year.

Drought-like conditions this summer, particularly in the northcentral part of the state, may dim the colors there, but likely not here.

“We had a really dry August, but then we got a little bit of relief,” explained Marc Abrams, professor of forest ecology and physiology at Penn State University. “I was prepared to say if that drought had continued into September we might have been in trouble. The trees were just on the border. Some leaves were turning.”

The drought was hardest in the northcentral part of the state, “so we may see a less defined

peak in the second week of October there,” Abrams said. “But the rest of the state should have a normal, showy autumn foliage display.”

For more than two decades Abrams has studied how precipitation and temperature influence timing and intensity of fall colors. He’s found that the critical period for coloration in the Keystone State runs from the middle of September to the second week of October. “At that point, we need nice cool nights in the middle to high 30s — but not a hard frost — and bright sunny days,” he said.

Ironically, drought in September and early October is generally good for fall colors, but not when the previous July and August is so dry, like this year.

Cooler temperatures signal deciduous trees to stop producing chlorophyll, the green pigment responsible for photosynthesis, Abrams explained. Photosynthesis is the way plants trap light energy and convert it to sugars and starches, the food and building materials for plants.

As the chlorophyll breaks down and disappears, it unmasks other leaf pigments. These other pigments — called xanthophylls and carotenes — create the glowing yellows and oranges seen in the leaves of yellow poplar, hickory, sycamore, honey locust, birch, beech and certain maples. After chlorophyll production stops, trees also produce another pigment in their leaves called anthocyanin. The anthocyanins create the brilliant reds seen in red maple, sassafras, sumac and black gum.

“Laboratory and greenhouse research indicates that more anthocyanin is produced when starch levels in the leaves are high,” Abrams said. “Because drought reduces photosynthetic rate — which in turn decreases starch levels — people generally believe that drought affects fall coloration in a negative manner.

“But is has to be a very prolonged and severe drought,” he said. “We’ve had a number of summer droughts in the last 20 years, and as long as we get that nice cool-down period, starch levels have been adequate to produce good color.”

Just how well the colors show is no small matter. It adds up to dollars and cents.

Statewide, Pennsylvania accounts for roughly 13 percent of fall foliage tourism around the country each year, according to the American Automobile Association.

Kevin Parsons, assistant director of the Crawford County Convention and Visitors Bureau, said he and his colleagues are already fielding calls from fall foliage tourists from outside the area who are planning local trips. On Friday, he said, he was paid a visit by a couple from New Hampshire — a national foliage hotspot in its own right — who were on their way through Crawford County on a statewide foliage tour along Route 6.

“I know we’re becoming more and more of a popular destination for leaf-peepers,” said Parsons. “We’re giving New Hampshire a run for its money.”