CARIBOU, Maine — This winter is officially going down in the books as the warmest winter on record in the Caribou area, with an average temperature of 21.6 degrees, officials at the National Weather Service said Monday.

In Bangor, where the average temperature over the last three months has been 26.8 degrees, the winter was the fourth-warmest on record.

The meteorological winter is defined as the three-month period from December through February, according to Francis Kredensor, meteorologist with the weather service in Caribou. He said Monday that the Caribou average of 21.6 degrees was 7.6 degrees above the 30-year average. It surpassed the previous record warm winter of 2009-2010 by six-tenths of a degree.

“El Nino is playing a part in this warming trend, because during the El Nino years there are always changes in the atmosphere,” said the meteorologist, referring to the weather phenomenon caused by periodic warming in areas of the Pacific Ocean. The changing ocean temperatures can alter atmospheric conditions and affect weather patterns around the world.

The warmer temperatures in Maine this winter were “not entirely caused by El Nino, but it is playing a part,” Kredensor said.

The top five warmest winters in Caribou, where records date to the 1940s, all have occurred since 2000, according to the weather service.

In Bangor, the average temperature this winter was 5.5 degrees above average.

Weather records date to 1925-26 in Bangor, where the three warmest winters before this year all occurred in the 1930s.

“It is tough to say why there is such a temperature disparity between Caribou and Bangor,” Kredensor said Monday. “It all has to do with the weather in each individual city and everything from differences in wind direction or whether there were more cloudy days in one place. In terms of snow, Bangor had a good 4 more inches of snow down there this month, so that had an impact as well.”

According to figures provided by the National Weather Service in Caribou, only 11 nights since Dec. 1, 2015, have had temperatures below zero, the fewest ever.

In comparison, February 2015 was the coldest on record measured in Caribou, with an average temperature of 2.8 degrees, which was 11.8 degrees below normal, while this February was the 10th-warmest on record, according to provided data.