It's almost leaf peeping season — but when will Utah's fall colors arrive?

A person walks through the fall foliage by Memory Grove Park in Salt Lake City on Oct. 12, 2021. Utah's fall colors are expected to come to life near the end of September, according to SmokyMountains.com.

A person walks through the fall foliage by Memory Grove Park in Salt Lake City on Oct. 12, 2021. Utah's fall colors are expected to come to life near the end of September, according to SmokyMountains.com. (Carter Williams, KSL.com)



Estimated read time: 4-5 minutes

SALT LAKE CITY — Utah is now in meteorological fall despite what your thermometer said throughout the first week of September.

That means the leaf peeping season is just around the corner. It's an especially wonderful time to venture out into Utah's wilderness to see its foothills, mountains and valleys covered in a mixture of yellows, oranges and reds.

"I think fall is the most spectacular time to be out in our mountains in Utah," says Darren McAvoy, an assistant professor of forestry at Utah State University-Extension and the university's forester.

These colors are the result of trees closing down photosynthesis ahead of the winter. As this happens, chlorophyll — a product in the process that turns leaves green — is no longer produced, resulting in a tree's "true colors" appearing. This typically begins when warm days are followed by cool evenings.

But even with all that's known about fall foliage, projecting when the leaves will change or the quality of the color isn't an exact science. The website SmokyMountains.com is among a few organizations that try to crack the code every year.

The map originated in 2013 after visitors inundated staff members with questions about when the Smoky Mountain region's fall colors would arrive, said David Angotti, the website's co-founder. But its projections also spread to the rest of the contiguous U.S., including Utah.

Angotti explains that the website uses the National Oceanic and Atmospheric Administration's historical records and long-range forecasts along with previously reported peak trends to generate a projection of when leaves will peak throughout the country. The website also tweaks its map in the fall, based on observational reports from website users.

When will the leaves peak in Utah?

This year's model, released last week, points out that there is some "minimal" turn along the Wasatch Front. But it projects the northern half of Utah will really begin to experience partial, patchy and possibly even near-peak conditions as early as the final week of September.

The rest of the state is forecast to be engulfed in color throughout the ensuing weeks, as parts of the state reach peak by mid-October. The northern part of the state is currently projected to reach past peak by the end of October, while the rest of the state will catch up to that by early November.

The Utah outlook is very similar for those looking to venture out to other parts of the West. Most parts of the region are expected to reach peak — or even pass it — by mid-October. The Southeast, which generally has the latest fall color peaks in the nation, is projected to peak in November.

How will this week's —and year's — weather impact the colors?

Utah's September heat wave smashed both daytime and overnight high-temperature records for a little over a week, so there really haven't been any cool evenings to trigger the end of the photosynthesis process, McAvoy explained. But with the end of the heat wave here, he expects it won't do too much, other than prolong when fall foliage arrives by a bit, in many areas.

"It could delay things just slightly," he said. "The hot and dry air could dry the leaves out a little bit before they have a chance to change color. That might mute the colors a little bit."

The upcoming autumnal equinox on Sept. 22 should also aid in the color-changing process. That's when there will be a shift with more nighttime than daylight, offering those cooler evenings needed for the change — as long as it doesn't get too cold at any point in the next few weeks.

Again, predicting fall colors isn't an exact science so it's difficult to know what to expect this fall. However, McAvoy believes the late-spring storms in northern Utah and a robust monsoonal moisture pattern in southern Utah this summer could be enough to make a close-to-normal-looking fall across the state when the leaves do change.

"That will help preserve the colors," he said, of the moisture. "Some years when we have bone-dry summers, the leaves are already so dried out that they aren't going to produce that much color. But I'm not seeing much of that this year — we've had enough moisture. It's really variable as you move around the state, of course, but depending on where you are, it seems the amount of moisture we've had might point toward a fairly-average fall color season."

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Carter Williams is an award-winning reporter who covers general news, outdoors, history and sports for KSL.com. He previously worked for the Deseret News. He is a Utah transplant by the way of Rochester, New York.

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