Vivid fall color expected in coming days

Earlier in September, it was becoming a bit unclear how drought conditions and a very warm and muggy summer would impact our fall color this year.

Some recent rains and a drop in temperatures, especially at night, have helped improve the forecast for some more spectacular colors. Already, some color is beginning to show such as cottonwoods, sycamores, black walnut and even some poison ivy.

Most of the state parks in the region are seeing changing colors, according to the Ohio Department of Natural Resources.

Cool nights and shorter days are what really begins to allow for trees and plants to begin to show their hidden beauty. The process that starts the cascade of events that result in fall color is actually a growth process. In late summer or early autumn, the days begin to get shorter, and nights are longer. Like most plants, deciduous trees and shrubs are rather sensitive to length of the dark period each day. When nights reach a threshold value and are long enough, the cells near the juncture of the leaf and the stem divide rapidly, but they do not expand. This abscission layer is a corky layer of cells that slowly begins to block transport of materials such as carbohydrates from the leaf to the branch. It also blocks the flow of minerals from the roots into the leaves. Because the starting time of the whole process is dependent on night length, fall colors appear at about the same time each year in a given location, whether temperatures are cooler or warmer than normal.

During the growing season, chlorophyll is replaced constantly in the leaves. Chlorophyll breaks down with exposure to light in the same way that colored paper fades in sunlight. The leaves must manufacture new chlorophyll to replace chlorophyll that is lost in this way. In autumn, when the connection between the leaf and the rest of the plant begins to be blocked off, the production of chlorophyll slows and then stops. In a relatively short time period, the chlorophyll disappears completely. This then allows for the true autumn color to be revealed.

Over the next 2 weeks, we can expect to see a rapid transition with lots of fall color thanks to the recent chilly nights. However, a frost would likely end the coloring process and cause leaves to just drop off the trees.

It is important to note that Ohio law requires residents to not burn leaves or debris, or even have any camp fires from the hours of 6 a.m. to 6 p.m. in the months of October and November.

As we enjoy the fall colors, our weather team is quickly working on our winter weather outlook in which I hope to share with in the next few weeks. It is hard to believe winter is right around the corner.

Eric Elwell is WHIO StormCenter 7 Chief Meteorologist. Contact him at or follow him on Facebook and Twitter.

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