SALT LAKE CITY (ABC4) — Despite the first snow of the year falling upon Utah’s ski resorts in both Big and Little Cottonwood Canyon, there is still an entire season between summer and winter.

That’s right: Fall. The season of sweaters and pumpkin spice. It’s also the season when Utah’s northern mountains are overtaken by brilliant fiery shades of red, orange and yellow as trees change color.

So when can Utahns expect the leaves to change color? That largely depends on where the trees are but according to the Farmers Almanac, peak fall colors in Utah will arrive throughout October. The Almanac says peak fall colors begin on Oct. 5 and could last about two weeks until Oct. 21.

A Fall Foilage prediction map presented by smokymountains.com, however, says Utah County could start seeing leaves change as soon as today. The map suggests Utah County trees will start seeing a minimal change in color on Monday, Sept. 4. By Sept. 11, Utah County’s trees will be “patchy” while several other counties in northern Utah begin showing minimal change. By the end of September and into October, Northern Utah will covered in partial fall color leaves and Utah County will be “near peak.”

Why do leaves change color?

What ignites the trees to erupt into reds, oranges and yellows is largely the length of day, Brad Hutnik, a forest ecologist/silviculturist with the Wisconsin Department of Natural Resources told Nexstar. 

We’ve been slowly losing daylight since the summer solstice in mid-June, and it will only become more noticeable as we move through September. Our trees are tuned into that lack of light and will begin to wind down for the year. 

“Oftentimes, by the time we’re seeing the leaves on the trees, that tree is functionally shut down for the year, and those leaves are essentially just dying off,” Hutnik says. By late September, many trees will have fully shut down.

“Every year, we see leaf change at about the same time,” he explains. “Some years it feels a little early, some years it feels a little later, but that’s really where other factors come into play that will maybe speed things up or slow things down.”

That includes drought conditions. Drought-stressed trees could change colors and lose their leaves sooner, Hutnik says. But a bit of rain could help slow that process, which can lead to variations in the colors in different regions. Since last winter, Utah has had little concern for water as drought conditions pale in comparison to past years.

As of the latest drought monitor report, 11% of Utah is in Moderate Drought compared to a year ago when 61% of the state was considered to be in Severe Drought. A strong winter, summer monsoon moisture and even heavy rains from a rare West Coast hurricane have helped ease Utah’s water woes. This also means Utah trees may take some time before showing their fall colors.

There may even be some trees that seem as though they are holding onto their leaves for dear life, well after their fellow deciduous pals have shed theirs. In that case, it’s safe to say that tree isn’t from the area.

As Hutnik explained, the tree was likely brought from another area that has a longer growing season.

“It’s not really responding to that length of day,” he said. “It’s a little bit out of sync.”

Similarly, fall can serve as a good time to spot an invasive species, particularly invasive shrubs. These invasive plants won’t catch onto local cues native plants are tuned into, Hutnik said. This means they will hold onto their leaves late into the year and may get their leaves earlier in the spring.