That smell in the morning air isn't the beginning of another wildfire "summer of smoke," at least not yet. It's left over from dozens or more controlled burns in the counties around Charleston and the remnant smoke getting trapped in the atmosphere overnight.

The phenomenon is called temperature inversion: Warmer air aloft seals off colder air from rising. "Usually at night, when the inversion sets up, you'll get some residual smoke that gets trapped," said meteorologist Brett Cimbora, National Weather Service, Charleston.

The weather conditions have the S.C. Forestry Commission limiting somewhat the acreage that can be burned and requiring fires be extinguished at night. So far, they and S.C. Health and Environmental Control officials say they have had no complaints. Under state law, burners must comply with management guidelines that set limits depending on weather and the distance of the burn from populated areas.

Among the areas with sizeable burns under way Thursday were Bonneau Ferry, Mepkin Abbey and Bluff Plantation in Berkeley County, said Scott Hawkins, of the Forestry Commission. More than 60 fires were burning in the coastal counties among some 120 statewide, Hawkins said. Smaller debris burns in the area could also be contributing to the smell.

Controlled burns are late-winter fires set by forest owners to clear away the thatch -- dry pine needles, leaves, limbs and other combustible material piled on the ground. The burns help prevent wildfires.

In 2011, hundreds of thousands of acres burned or smoldered in the four Southeastern coastal states. Fueled by drought and winds, forests went up like tinder. The fires hazed and smelled up the Lowcountry air for months. It started in late March when wildfires took out some 3,500 acres in Charleston and Dorchester counties in the same week. The worst of it was fires in the vast Okefenokee Swamp in Georgia that burned more than 300,000 acres and sent plumes of smoke up the coast on prevailing winds.

Foresters are concerned that the ongoing drought could mean another summer of blazes. "We are bracing for an active fire season unless rainfall and drought conditions improve," Hawkins said.

Reach Bo Petersen at 937-5744 or follow him on Twitter at @bopete.