LITTLE ROCK, Ark. — A tornado fueled by an unusually warm winter air sliced through parts of northwestern Arkansas early on New Year’s Eve, killing three people, injuring several others and knocking out power to thousands of homes and businesses.

The dead were killed at Cincinnati, a hamlet of about 100 about three miles from the Oklahoma border. Washington County sheriff’s dispatcher Josh Howerton said the storm touched down near the center of the community. He said “lots of injuries” were reported, and officials in nearby Benton County said the storm injured two people and damaged five homes there.

Several flights to and from the Northwest Arkansas Regional Airport at Highfill, in Benton County, were delayed or canceled Friday morning as officials worked to clear storm debris littering the runway.

The region has been bracing for severe weather for much of the week. Gulf moisture riding southerly winds pushed temperatures into the upper 60s and 70s on Thursday — ahead of a cold front expected to drop temperatures into the teens by Saturday morning.

“Anytime you have a significant change in air mass there is going to be unsettled weather marking the two different air masses,” said Joe Sellers, a meteorologist with the National Weather Service office in Tulsa, Okla.

Rick Johnson, the deputy emergency manager for Washington County, said the same storm system caused damage in nearby Tontitown, but emergency responders had trouble reaching the damaged areas because of downed power lines.

The Tulsa weather office issued a tornado warning for Cincinnati and area towns at 6 a.m., nine minutes before the storm hit.

Later Friday morning, in south-central Missouri, baseball-sized hail was reported north of Mansfield in Wright County.

“This storm system has been showing significant signs that it could develop,” said Chris Buonanno, a meteorologist at the National Weather Service in North Little Rock who was monitoring the storms as they moved deeper into Arkansas. “Conditions are favorable for seeing a severe outbreak.

“In the winter you don’t always have the instability” that would allow tornadoes to develop, Buonanno said. “This time, we have the instability.”