Cape Codders by the hundreds were asking themselves and their fire departments Tuesday night, "What's that funny smell?"

An odor variously described as burning rubber, burning electrical outlets, burning car brakes and melting plastic was reported to fire departments from Eastham to Bourne.

Firefighters in full turn-out gear from department after department searched their towns with no luck. That is until around midnight, when a radio broadcast from the Barnstable County Sheriff's Department came up with a possible answer: temperature inversion.

Simply put, a temperature inversion can occur when an oncoming cold front pushes a warmer air mass in front of it, then sits on top of the warmer air mass, said Alan Dunham, a National Weather Service meteorologist in Taunton.

In this case, the temperature inversion brought the stink from someplace else and dropped it on our doorsteps.Then that cold front sat on the stink for a couple hours.

"The conditions were just right for that," Dunham said of the Tuesday night weather event. "We had this hot humid air, pollution or smoke particles from elsewhere just attach themselves to that and linger here."

In the case of the acrid smell assaulting Cape sensibilities, the possible source has not been pinned down.

It could have been residue from North Carolina where, Sunday and Monday, firefighters battled more than 300 brush fires that forced the evacuation of homes and burned 9,000 acres.

Or it could be pollution from New York City.

"I can't say for certain that it was the fires in North Carolina or anything else," Dunham said. "But it is possible. We had similar reports from southern Rhode Island."

Inverted temperatures are not all that rare, Dunham said, but once in a while they get noticed by the general population because there is a smell associated with them.

"A number of years ago, there were big fires in Canada and that brought smoke down through Vermont, Maine, New Hampshire and Massachusetts because of inverted temperatures," he said.

On the Cape, calls to fire departments seemed to cluster about the time the Celtics crashed and burned in Los Angeles - shortly before midnight. In Sandwich, calls came from all areas of the town.

Eastham firefighters similarly searched their town and at one point, called the Coast Guard wondering if there were a ship burning off the coast.

Staff at the county communication center sent dozens of calls to fire departments in a relatively short period of time. Then from the dispatch center came relief to many departments - a probable explanation for the smell.

"We can't take the credit. We're just the middle man," said Peter Thomas, director of the county communication center which dispatches fire calls for seven Cape departments. "We got a call from Bob Crocker. He put it together - a temperature inversion."

A 26-year veteran of the state Department of Recreation and Conservation, Crocker is a district forest fire patrolman at Shawme Crowell State Forest. Much of his training as a wild land firefighter focused on weather conditions. "Wind, rain, terrain, slope - all of that factors into your firefighter training," he said.

He was getting ready to turn in for the night Tuesday when he heard an explosion of calls on his home scanner sending departments out on smoke investigations.

"I got on my computer, checked out the weather channel and saw a cold front coming in from around New York," he said. "I just figured out what it was before anyone else had a chance," he said. "I didn't solve a mystery or a problem. I just passed a little information along."