It’s officially fall, and with it comes amateur predictions on how this year’s weather will impact fall colors.
Such predictions are rarely rooted in fact, according to local experts who broke down common myths surrounding the yearly phenomenon. The truth is much less variable than the average Coloradoan might realize.
“The window shifts a little bit here or there, but honestly … the timing is never wildly, dramatically different,” said Irene Shonle, Colorado State University’s El Paso County extension horticulture agent. “Maybe it’s a week here or there, but that’s about it.”
One of the most common misconceptions, according to Shonle, is that a few trees turning color in August indicates an early season change overall. It doesn’t work that way, she said, and there will always be a handful of trees that change earlier than others.
In reality, Colorado is more likely to experience a slight delay in fall colors this year due to continued warm temperatures, Shonle said, but that’s not the primary driving force behind trees’ change.
Daylight plays the most important role in triggering fall foliage, according to Colorado State Forestry Service entomologist Dan West. As days get shorter, trees begin to “shut down” and prepare for winter.
This timing is fairly standard every year. Vibrancy, however, is a more challenging prediction.
Good winter snowpack followed by abundant spring and summer rainfall provide optimal leaf growing conditions. Warm, dry September days with cool — not cold — nights are also key, burning away the green chlorophyll pigment. These conditions prevent browning on leaves’ edges.
“If we can get kind of that abundant sunshine coupled with cool nights, it’s going to produce the most vibrant color patch that we could possibly see,” West said. “However, in Colorado, storms come and go, right? And so, looking at the ideal condition is great, but in realty we still get storms that roll through.”
Frost and snowfall can cause the greatest year-to-year change in fall colors, throwing a wrench in even the greatest of expert predictions.
People underestimate the impact of a late-season spring frost, West said. Many of a tree’s leaves will turn black and die in the event of a late frost, forcing it to push out new leaves and putting it behind its natural developmental schedule.
An early frost in the fall has a similar effect. The earlier a hard fall frost, the lower the chance of strong fall colors.
“Things could end abruptly in early October if we got one of those early snows,” Shonle said.
Weather conditions over time also have a hand in determining vibrancy, according to West.
Colorado experienced several severe droughts in recent years. Although 2022 presented a bit of a moisture rebound, West said it was still below average. It remains to be seen if the summer rain was enough to counteract the lack of moisture in drought-stressed trees.
This all makes for a “somewhat variable” season, West said, but he holds out hope for some good fall color viewing — barring an unexpected freeze.
If those searching for brilliant colors aren’t finding what they’re looking for, he suggests driving an extra 5 or 10 minutes down the road, where conditions might be entirely different.
“With the variable precipitation that we got as well as some of the pests that we know are out there, I think that just a little bit of patience and a little bit more time will get people a great show,” West said.