Carter Williams, KSL.com, File

Looking forward to Utah’s fall colors? Here’s what to expect this year

By Carter Williams, KSL.com | Updated - Sep 18th, 2019 @ 5:25pm | Posted - Sep 18th, 2019 @ 1:12pm



SALT LAKE CITY — Sure, it’s not quite fall yet — the autumn equinox isn’t until the early hours of Monday — but now that summer is all but over, it’s time to gear up for the season. That means it's time for pumpkin-spiced everything, scary Halloween decor, sweaters, football and, of course, fall foliage.

There aren’t many things quite as pleasant as absorbing a vista of golden-yellow, scarlet or orange trees. It’s even better when it’s the reward at the end of a strenuous hike.

While Utah’s fall colors don’t garner the same attention as the American Northeast or the upper Midwest, Utahns know similar splendor can be found in the Beehive State. So when can we expect fall colors coming into play this year?

Why we get fall colors

First of all, there’s a science behind these tremendous views. It starts with chlorophyll, which is a key player in photosynthesis that produces carbohydrates needed for growth, as noted by the University of Vermont Department of Plant and Soil Science.

Chlorophyll is why leaves are green throughout spring and summer. That’s the color we see when it masks carotenoids or anthocyanins, which are other pigments that create yellow, orange, red or reddish-purple hues. Different trees have different pigments that some refer to as the tree's "true colors."

Once cooler temperatures arrive and the days get shorter, production of chlorophyll slows down and the other pigments in trees slowly appear before the leaves fall to the ground.

How weather factors into the season

Foliage forecasts can be made by looking at current and long-range forecasts, but it isn't an exact science. That's due to meteorology only really giving a clear enough picture about a week in advance, as compared to an entire season. Therefore, it’s difficult to know exactly when this process will begin, but the weather does factor into the colors we see.

“A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring about the most spectacular color displays,” according to the U.S. Forest Service's website. “During these days, lots of sugars are produced in the leaf, but the cool nights and the gradual closing of veins going into the leaf prevent these sugars from moving out.”

The forest service says soil moisture also affects fall colors. For example, a late spring or a summer drought might delay fall colors up to a few extra weeks. A warm period during fall might lower the vibrancy, but those warm sunny days followed by cool nights also help produce better colors.

It's also not uncommon for snow to begin in higher elevation areas in September, which happened last week in the Uintas and Cottonwood canyons of northern Utah. Snow can also factor into this. Weather.com meteorologist Brian Donegan wrote that snow could bring down trees or cause their leaves to fall prematurely.

Utah's 2019 weather and possible impact on fall colors

To recap Utah's 2019 weather to this point, almost everything has been pushed back a month, said National Weather Service hydrologist Brian McInerney.

"Our spring was so cold and so wet that we really didn’t start the monsoonal flow, we really didn't start when you’d see a normal weather pattern that starts about July 1," he said. "We were about a month late on the monsoon. We didn't see much of it this year. It started late. Then it got hot in late August and dry. ... And now the question is: Is that same push going to make the fall hot and dry like we saw in summer, or is the monsoon going to kick in?"

There are other factors, as well. Fires, debris flows and mudslides in Utah's various canyons will likely factor into the equation, McInerney said.

As for color vibrancy, there isn't much of a way to predict that if the weather is still unknown. Therefore, it's still unclear how Utah's wacky 2019 weather will play into the fall foliage color. In fact, David Bowling, a professor in the School of Biological Sciences at the University of Utah, said he and fellow professors often field calls from others seeking to know in advance and they don't have an answer.

As he said, there is still lots to learn about plants. He also explained warmer temperatures — like what Utah experienced to start September — would indicate the season being pushed back. Fall colors get pushed back when there are warmer temperatures because that helps continue photosynthesis production, and thus chlorophyll is still masking other pigments.

Temperatures have bounced back and forth since the first week of September and Bowling added as long as Utah doesn't experience a sudden cold snap, the colors likely will have a chance of being aesthetically pleasing.

"Plants have to slowly adjust to cold temperature and if it were to get super, super cold like 20 degrees next week, we may not even get any fall colors at all," Bowling said.

Luckily, current forecasts have temperatures in Salt Lake City, as an example, dropping to the 60s by the end of the week. They will likely rise back into the 70s after that.

When should we expect peak fall colors in Utah this year?

The first fall colors forecast that made its rounds online came from SmokyMountains.com in late August. In its yearly fall foliage map, the website predicted northeastern Utah to peak in early October, central Utah to peak close to mid-October, and southeastern Utah to peak shortly after that.

That actually would be close to Utah's normal pattern. The Weather Channel's forecast for fall colors, which was released last week, projects something similar. It has colors predicted to peak in early October for eastern Utah and mid-October for the rest of the state.

Another site, New England Foliage, which tracks national foliage daily, reported trees in parts of northwestern Utah have begun to turn, which is in line with the predictions.

So, if those projections hold true, don't forget to map out your hikes on your fall to-do list in the coming weeks, in addition to purchasing Halloween candy and pulling your sweaters out of the closet.

Carter Williams

KSL Weather Forecast