The National Weather Service Office in Tucson has begun a countdown to the warmest year on record, despite the little dip in temperatures that sent us scrambling for sweaters Monday.

The Weather Service Monday warned of a hard freeze overnight in Cochise, eastern Pinal and Greenlee counties, where temperatures got down to 25 in a few places Monday morning.

Parts of the Tucson metro area could also drop below freezing briefly, said Weather Service meteorologist John Glueck.

In Tucson itself, overnight temperatures in the mid-40s might call for a blanket, but are only a couple degrees below normal.

We’ll be back to normal by Wednesday and above-normal on Thursday through the weekend, according to the Weather Service forecast.

It may seem cold, said Glueck, because this is the first cold wave of the season, but it would have to get much colder than this for a long time to keep us from setting a record for warmest year in 2014.

“We’re on track. I think it’s a foregone conclusion that were going to set a record. We’d have to be really, really cold for the next 45 days not to break the record,” Glueck said. If we do set a record, said Glueck, it will be courtesy of our warming nights.

Low temperatures have been inexorably climbing higher. The trend since the 1960s tracks pretty clearly with population growth, Glueck said.

Glueck said that demonstrates the “urban heat island effect.” Buildings and asphalt retain the day’s heat longer than natural areas.

The warmest year on record in Tucson was 1989, with an average temperature of 71.4 degrees. This year, as of Monday, the average is 74.6 degrees.

Contact reporter Tom Beal at tbeal@tucson.com or 573-4158.