The shorter amount of daylight is the primary trigger for the color change. As the nights become longer and chillier, the chlorophyll production slows and eventually stops. Without chlorophyll, the yellow and orange pigments of the leaves become dominant, resulting in the many beautiful colors of fall.
Warm, sunny days with cool nights are the ideal conditions for a colorful change. Soil moisture is also important. Both drought and excessive rainfall can be detrimental to a spectacular foliage season. September in the Miami Valley was one of the wettest on record, according to data collected by the National Weather Service.
During a big part of the summer and then well into October, much of the Ohio Valley and parts of the Midwest experienced unseasonably warm temperatures and muggy conditions. There were several nights during which Dayton, Cincinnati and Columbus had record high nighttime (low) temperatures.
MORE FROM ERIC ELWELL: 2018 on track to be one of the warmest in years for Miami Valley
The stretch of warm nights has dramatically slowed the departure of the chlorophyll leaving the leaves of trees, thus slowing their change to the vivid reds, yellows and oranges we’ve learned to love.
It is appearing more likely that the fall color this year, while delayed, will also likely not be as vivid. Now that temperatures have finally dropped, the potential for frost has also increased. While cool nighttime temperatures are ideal for enhancing autumn colors, a couple of hard frosts would immediately end the color change and the leaves would turn brown and fall from the trees.
Also, as we approach November, storm systems that impact the Ohio Valley typically become more intense, containing higher wind speeds. This will also tend to rip leaves off of trees before the color process can complete.
But while the outlook for vivid fall colors may not be as bright as we’d like, the fact is the weather conditions have improved for the transformation to really get underway. If we are lucky in the coming one to two weeks, any frosts will be light and strong winds will stay away.