How Weather Affects Fall Leaf Colors (Credit: Climate Central)

Photo taken in the end of November 2015 on top of Mt. Mitchell in North Carolina at the end of peak "leaf season". While some leaves are still in their vibrant fall colors stage, many have already fallen at this point in the year in this area.

As September comes to an end and we enter October, many people are excited about the transition into fall and all of the joys that come with this season and its cooler weather.  Pumpkin flavored everything has already made its appearance, stores are filled with Halloween-related decorations and costumes, and many people are already longing for the weather to cool down enough for their cozy fall sweaters.  One other major fall highlight that many are looking forward to? The spectacular colors brought on by the leaves changing.  So why do leaves change colors in the fall and how might variations in the weather alter how they change?
 
The coloring in leaves is determined by the amount of chlorophyll within the leaf.  Chlorophyll is used by the plant to turn the sun’s rays into energy and is what gives leaves their green color.  In the fall, leaves produce less chlorophyll as the days get shorter and cooler, causing them to lose that green color and change into the bright orange, red, and yellow leaves that paint fall landscapes.  Weather can be used to estimate when the peak “leaf season” will be in various areas since temperatures and rainfall amounts can play a role in when leaves turn and how quickly they will fall from the trees.  Drought can cause leaves to turn more quickly and appear less vibrant. On the other hand, too much rain in the summer can also bring about the changing in colors more quickly as excessive rainfall can be a stressor to the trees. Moderately warmer temperatures can cause a delay in the changing colors, however, excessively warm temperatures could cause the leaves to change colors rapidly and fall sooner, causing the beautiful fall colors to disappear more quickly.  An overall increase in temperatures could also cause more variability in when the leaves change, making it harder to predict when they will reach their peak colors. 

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©2019 Meteorologist Stephanie Edwards