Fall foliage enthusiasts might not have as much vibrant leaf color to look at again this year — owing to a hot, dry late summer and early fall.
“A lot of it has to do with the record or near-record temperatures we’ve had in late September, early October and also the very severe drought over the last 30 days,” said Marc Abrams, Penn State professor of forest ecology and physiology. “We’ve been getting a little bit of rain lately, but through September was exceptionally dry, about 25% to 75% below average precipitation.”
Those weather patterns are causing early, muted leaf color, early leaf drop and — paradoxically — a delay in some leaf color changes, he said.
During the summer months, meteorologists and ecologists were predicting good color for fall foliage due to adequate rainfall in the spring and early summer followed by drier, sunnier weather.
Color is better “when you get a nice wet spring and early summer and it starts to dry out ... as long as the temperatures don’t get too warm,” said Paul Pastelok, Accuweather senior meteorologist.
The late summer drought caused leaves to “die off a little bit too fast” in some areas, he said. Warmer fall weather also “allowed for greening to occur to delay” the color changes.
Leaves that have already changed color will not be around in mid-October for “peak” foliage colors, Abrams said. Other leaves will have delayed color changes.
“Warm temperatures extending well into October will cause a delay in the fall colors because it basically keeps the leaves in a green condition and delays the breakdown of the cholorphyll,” he said.
The early October frost this past weekend also concerns Abrams, because frost kills leaves quickly rather than letting them die slowly and change color. Early frosts have a tendency to change green leaves straight to brown, he said.
In Pennsylvania, he said, the central, southeast and southern tier regions have borne the worst effects of the drought, and are seeing less vibrant fall foliage as a result. Conversely, the northern and western tiers will fare better in leaf color, though most likely still below average.
State College is seeing less vibrant foliage compared to some of its suburban areas and more mountainous parts of the county, said Pastelok, because of the sunlight and warmth it received in the middle of the valley during late summer. Outside suburbs tend to cool off more at night and mountains tend to block sunlight, he said, allowing a faster breakdown of chlorophyll and more vibrant colors.
“My overall observation is that on average you can expect a good year ... in Pennsylvania, but great years are fairly rare and are more of a five or ten year event,” said Abrams.
Over the last decade, September “has turned out to be a warmer month and a sunnier month,” said Pastolek. Summers on the back end have lasted longer, he said, but “that could change over the next 20 years.”
Temperatures extending into mid-October, which is usually peak fall color season, are predicted “fairly warm” in the mid-60s during the day, said Abrams, but nights are predicted to drop to the 40s this week and down to the 30s in the third week of October.
“Some rainfall and a continuation of cool nights will go a long way to help save this fall season,” he said.
But there’s still hope for photographers and fall travelers hoping to catch a glimpse of colorful fall foliage.
“Good color will come through in places, and people should get out there and search out those places and enjoy the color,” said Abrams. “In 33 years of doing this, I’ve never seen a year devoid of good coloring.”