When early fall feels like summer, that will change how long trees will show off their seasonal colors.

Deciduous trees, explains Boyce Tankersley, director of living plant documentation, respond to environmental conditions when preparing to go dormant for the winter. Just like animals that hibernate, trees slow their processes down in order to conserve energy. What we can see of this process can be beautiful: leaves change from green to vibrant reds, oranges, and yellows. Then trees drop their leaves and wait out the winter.

In a regular year, trees aren’t in a rush to go dormant. The process that we see takes several weeks. The production of chlorophyll, which produces the green color in leaves, fades away, unmasking the beautiful colors we associate with autumn. As the season progresses, the leaves will eventually drop. In Chicago, our trees usually reach peak color in the first two weeks of October, and aren’t usually bare until late October or early November.

But sometimes, it isn’t a regular year. The heat can be a factor.

Expect color, but some years, the display is shorter than usual.

“The higher the temperature, the faster the processes go,” Tankersley said. And during a drought, leaves may drop only a few days into fall. If local rain gauges are virtually dry, with less than 2 inches recorded in the month of September, the trees will show it.

“Trees don’t have minds, but they do respond to environmental clues. If there’s been little rain, they will drop their leaves early in order to conserve water and get through the rest of fall and winter,” he said.

If you’re a fan of getting family portraits done with a backdrop of colorful foliage, Tankersley suggests getting those done sooner rather than later.

“Some years, we have to be a little bit more proactive about getting out there and getting photos as the trees come into color. They’re just not going to hold.”