Weather moves from west to east in the NWS Charleston Forecast Area, but fall foliage goes in reverse: from east to west, generally following elevation. Many factors affect its timing from year-to year. But on average, peak colors blaze the higher mountains of West Virginia in late September, and progress west through central West Virginia and extreme southwest Virginia in early October. Finally, fall foliage embraces the lower elevations of southwest West Virginia, northeast Kentucky, and southeast Ohio in mid to late October.

The colors are present within the leaves all summer, but the green pigment of chlorophyll overwhelms the others. Photosynthesis is the process by which sunlight is converted into food for trees. While chlorophyll is dominant in this process, other chemicals and their pigments are also involved. Carotenoids are responsible for yellow and orange colors. As nights lengthen, trees prepare for winter by shutting down their need for sunlight. The continual replenishment of green chlorophyll slows down and eventually halts in the fall, revealing the other colors. Additionally, leaves rich in sugar (including maples and oaks) develop anthocyanins in late summer, which show up as shades of red and even purple as the green chlorophyll disappears.

Trees take their color cue from longer nights, but how does the weather itself impact fall foliage? The ideal combination: a wet summer followed by a dry fall. Summer rain produces thicker, healthier leaves. Sunny fall days allow for more anthocyanin to be produced during the last few weeks of leaves, resulting in a wider array of color. Cloudy days, on the other hand, result in not enough anthocyanin for bright reds. With clear fall nights, an early frost (see graphic at right) causes the green chlorophyll to be broken down all at once, resulting in an earlier, more vibrant color change. This is why the higher elevations of our area have peak colors as early as late September.

Warm temperatures will make leaves turn color later in the fall, but also more abruptly (a shorter season).

Source: Charleston National Weather Service Newsletter, Written by Mark Pellerito.