Cooler nights, shorter days and lots of rainfall. Those are the ingredients that climatologists and foresters say are likely to create a spectacularly colorful fall foliage season in Oklahoma.

The brilliant orange and red hues that adorn hardwood trees in autumn usually peak in the state in late October and early November. But visitors to southeastern Oklahoma's Talimena Scenic Byway, one of the state's most traveled fall foliage drives that stretches from Talihina, Okla., to Mena, Ark., reported a light scattering of yellow last week in the trees of the Ouachita National Forest.

"It should be happening very soon," said Keli Clark, marketing coordinator for Oklahoma State Parks. Clark said leaf peeping makes autumn one of the state's busiest tourist seasons, rivaling spring and summer travel.

"People love to go out and look at the foliage. It's just beautiful," she said.

A growing season with ample moisture followed by a sunny autumn marked by warm days and cool but frostless nights provides the best weather conditions for development of the brightest fall colors, according to the United States National Arboretum. And the elements needed for vibrant autumn foliage in Oklahoma are starting to add up.

The National Weather Service said temperatures dipped into the 40s across the state for the first time this season Sunday morning. Lows dipped into the 30s in the far western Oklahoma Panhandle.

"We'll continue to remain close to seasonal temperatures," meteorologist Ryan Barnes of the National Weather Service in Norman said Sunday.

Increasingly shorter days mean that leaves are receiving less sunlight than they did during the hot summer months, causing the production of chlorophyll, which gives the leaves their green pigment, to become sluggish. And abundant rainfall the state has received this year assures that the leaves are primed for a vivid autumn display.

With more than two months left in the year, 2013 is already the fourth wettest year on record in central Oklahoma, Barnes said. As of Sunday, a little more than 48 inches of rainfall had been recorded, with some areas of the state receiving even more. The record rainfall total of 56.95 inches was set in 2007.

State Forester George Geissler said 2013 has the potential to be one of Oklahoma's better years for color changes, especially in eastern Oklahoma where the state shares a long forested border with Arkansas.

"But you do have trees changing color all over the state of Oklahoma," Geissler said. "When you get to this time of the year, it's not so much the cold but it's that the days are getting short and you're getting less light."

Aside from the Talimena Drive, the Beaver's Bend and Robber's Cave areas of southeastern Oklahoma are tourist destinations during the fall, Clark said. In northeastern Oklahoma, areas around Grand Lake and the Illinois River are popular.

But Clark said the northwestern part of the state, including the Great Salt Plains region, will be the first to experience nature's autumn displays. Various hardwood, locust, cottonwood, post oak, hackberry and willow trees in the area create a stunning canopy of radiant reds, yellows and oranges.

"Western Oklahoma can be just as beautiful," she said.