Drought leading to an earlier emergence of fall foliage

Changes in tree colors and leaves starting to fall have already been noticed in much of the state, but this is much earlier than the seasonal average.

Over the past 20-30 years, the seasonal average for the peak of fall foliage in the state of Missouri is mid- to late October. There are still a few days left in September, and changes to fall foliage have been ongoing for the past couple of weeks. This means these changes have come much sooner than expected.

Weather is one of the leading factors that affect the timing of fall foliage from year to year. Fall foliage tends to arrive earlier when drought has been in place or a lack of rainfall has been observed throughout the summer period. This is because the lack of water leads to a shortened time when the tree can sustain its leaves. The tree sheds its leaves sooner so that it can keep itself alive, which leads to an earlier onset of this fall foliage.

Heat stress can also play a factor, as excessive heat can make trees go through their water supply much faster than in more typical temperatures. Once they are running low on water, they shut down the other processes that keep the leaves alive, leading to fall foliage emerging.

Drought is one of the main factors influencing earlier fall foliage in Central Missouri. In August for Columbia this year, a total of 0.11 inches of rain was measured for the entire month. The average rainfall in Columbia for August in previous years is 4.14 inches, so this was a 4.03-inch departure from the normal.

In September so far, 1.97 inches of rainfall has been observed while the average from past years is 2.95 inches. This is also nearly an inch of rainfall that was not seen in Central Missouri. As of last week, a moderate to severe drought is in place for the majority of the state due to this lack of rain.

Heat stress has been another factor for fall foliage arriving sooner than usual. In August for Columbia, there were nine days when the maximum temperature was measured at or above 90 degrees. In September 2025 so far, there have been seven days when the maximum temperature broke this same threshold.

On top of this, the daily maximum temperature average over the course of this month so far is 3 degrees above the average of previous years.

The stress from the drought and heat can lead to less vibrant colors in the fall season since the trees have to act faster to preserve themselves. They are given less time to have more vibrant colors appear, and that is why leaves may be a bit more dull or brown.

The good news is that much-needed rainfall has been seen over the past week, so the process by which leaves change color and fall off the tree could be slowed slightly.