How the Weather Impacts Fall Foliage

Posted: September 23, 2015, 8:01 pm by jmartucci

As we head through October, the leaf colors are growing more vibrant with each passing week across the Northeast. While the shorter daylight and longer night hours help change the colors, did you know the weather plays a pivotal role in fall foliage? For beautiful colors, the region ideally needs a wet growing season (April – June), followed by a not too hot, not too cold summer and a fall with plenty of sunny days and cool nights. On the contrary, long dry stretches in summer and fall or excessive wet and warm days can put stress on trees and dull the colors. In addition, an early frost or freeze can have adverse effects with leaves quickly changing from green to brown with little, if any, transition.


(Apr - Jun 2015 Precipitation Departure. Courtesy of the Northeast Regional Climate Center)

Given the weather pattern from the spring to early autumn, will the Northeast fall foliage be vibrant or dull this year? As the above graph illustrates, the 2015 growing season featured rainfall extremes on both ends of the spectrum. Over the I – 95 corridor of New England and New Jersey, rainfall fell well below average while areas from upstate New York into the mid - Atlantic finished wetter than normal. Then, the Northeast experienced near perfect summer temperatures which supports vibrant fall colors. In September, the main weather pattern consisted of consecutive dry, warm and generally sunny days. While sunny September weather bodes well for colorful foliage, the lack of cool nights and excessive dry conditions along the I – 95 corridor impeded the progression of vibrant fall colors. In fact, the U.S Drought Monitor classified 58% of the Northeast as “abnormally dry” with nearly 9% in a “moderate drought” as of September 29, 2015. Of course, the heavy rain events during late September and early October helped put a dent in the rainfall deficits and decreased the stress on trees. While those in interior sections of the Northeast were also dry, it was not to the same extent as eastern areas, which also observed more frequent cooler nights.

To answer the aforementioned question, it really depends where you live. Those in far northern and western sections of the Northeast and in the mid – Atlantic are in store for vibrant colors this fall that peaks near the normal time. On the other hand, areas further east, closer to the I – 95 corridor in New England down into Central New Jersey and eastern Pennsylvania, should see near or slightly duller than normal colors. In addition, the lengthy dry spell in late summer and early fall will likely delay the peak of season by a few weeks. To learn when your area normally observes its peak in fall foliage, see the handy road map below. Maybe you will even complete the whole map!

 

Typical peak color dates in the Northeast. Expect the I-95 corridor to peak a week or two later than these normals.

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