Nature's multicolored display is just a few weeks away. There are three main factors that influence autumn leaf colors: leaf pigments, length of night, and the weather. While the timing of shorter days does not change, other environmental influences like temperature, rainfall and food supply vary from year to year, affecting biochemical processes in the leaves that paint the landscape.
A succession of warm, sunny days and cool, crisp but not freezing nights in late summer heading into early fall seems to bring about the most colorful displays. In these conditions, lots of sugars are produced in the leaf, but the cool nights and gradual closing of veins going into the leaf prevent the sugars from moving out. Lots of sugar and lots of light spur the production of brilliant colors.
This summer was warm without any prolonged, stressful heat. There was ample moisture, with most of the state seeing above-average precipitation. Summer drought could delay the onset of fall color by a few weeks or lead to an early dropping of leaves. After the weather from this summer, trees are healthy and thus should have plentiful sugars. As long as a flooding rain does not occur, an unusual heat wave, a violent wind storm, a snowstorm, or a series of early hard freezes, Montana's colors should be in good shape.
Because of variations in the weather, no two autumns can be exactly alike, but this one that we're heading toward should produce a feast for the eyes.
