Autumn harvest displays are popping up in yards and along storefronts throughout the Cleveland and Bradley County community, but the accompanying fall foliage rainbow of color is lagging just a little behind.

But not for long.

The traditional harvest season panorama should peak within the next week — maybe even the next few days — in higher elevations while the explosion of leafy tints should make its way to lower areas over the next 10 days.

According to the Cherokee National Forest website, “Things are starting to brighten up in the Cherokee National Forest at elevations above 3,500 feet. Colors have changed rapidly in the past several days.”

As recently as last weekend, the normal rainbow explosion in Gatlinburg and Pigeon Forge was little more than a tinted puff, but that’s changing quickly ... especially for travelers planning to hit the tourist attractions this weekend.

Dan Hartman, urban forester for the city of Cleveland, said the immediate local area should be seeing major fall foliage changes over the next couple of weeks. His assessment is the same as the national forest’s website which points out best fall color viewing can vary greatly from year to year.

In most cases, it’s a matter of moisture levels and temperatures but one secret ingredient to the foliage potpourri is daylight hours. As days grow shorter and shorter, the leaves change quicker and quicker.

“The factors that influence autumn leaf color are shorter day lengths, weather (primarily cooler temperatures and less moisture) and changing levels of leaf pigments,” the website explains. “The only constant factor from year to year is the shortening day length. As days become shorter and nights grow longer, biochemical processes in the leaf initiate changing leaf color. All the other factors vary annually, making the prediction of autumn color difficult.”

Hartman took it another step.

Too, he pointed to the difference in leaf-changing depending on elevation. In the mountains, it comes sooner; in the valleys such as Cleveland it is traditionally a little slower.

Drought stress, such as that witnessed in Southeast Tennessee for much of the summer and early autumn, also contributes to the timing of fall colors.

“A growing season with ample moisture that is followed by a rather dry, cool, sunny autumn that is marked by warm days and cool, but frostless nights, provides the best weather conditions for development of the brightest fall colors,” Hartman said. “Lack of wind and rain in the autumn prolongs the display. Wind or heavy rain may cause the leaves to be lost before they develop their full color potential.”

The Cleveland area has experienced all the components in Hartman’s formula with the exception of ample moisture in the growing season. Last spring started with plenty of rain but conditions dried quickly into the early summer and all the way through it.

The Cherokee National Forest website recommends three primary routes locally for fall foliage appreciation.

They include:

n Ocoee Scenic Byway: The first National Forest Scenic Byway in the nation traditionally lives up to its name each autumn. The Byway is located in Polk County and consists of segments of two roads. Seven miles of the Byway travel up Forest Service Road 77 to Chilhowee Mountain. The remaining 19 miles of the Byway follow U.S. Highway 64 through the Ocoee River Gorge and beyond the site of the 1996 Olympic Canoe & Kayak events.

n Cherohala Skyway: The Skyway travels along U.S. Highway 165 from Tellico Plains to Robbinsville, N.C. This route offers panoramic views with elevations reaching more than 5,000 feet.

n Hiwassee River/Mecca Pike: From U.S. Highway 411 north of Benton take State Route 30 east to Reliance. This route follows the winding Hiwassee River. At Reliance, take State Route 315 across the river and head north. At the intersection of Mecca Pike (State Route 310/39) near Jalapa there are two options: Turn west (left) onto Route 310 and head toward Etowah and Highway 411; or, turn east (right) onto Route 39 and go toward Tellico Plains.

For those interested in the “science” of fall foliage colors, Hartman offered a crash course.

“During the growing season, chlorophyll is replaced constantly in the leaves,” the forester explained. “Chlorophyll breaks down with exposure to light in the same way that colored paper fades in sunlight. The leaves must manufacture new chlorophyll to replace chlorophyll that is lost in this way.”

He added, “In the fall of the year, the connection between the leaf and the rest of the plant begins to be blocked off. The production of chlorophyll slows and then stops. In a relatively short time period, the chlorophyll disappears completely.”

This is when fall colors are revealed, Hartman said.

Here’s a breakdown of the tree leaves and their colors, according to fall foliage sites on the Internet. Hickories and poplars usually turn yellow; maples anywhere from yellow to red to orange; oaks from red to brown; beeches usually yellow; and sweet gum anywhere from yellow to dark red.