Valentine's weekend outlook: Down to zero?

As we've posted, if you like snow but don't particularly like the cold, this has been your winter to date. Ironically, in the end it will rank among the warmest and among the snowier, a rare combination.

And while Tuesday's snow falls at the rate of about an inch a month, and we wait for whatever else is coming while the weathermen sweat bullets, we will speculate on another potential irony:

During one of the warmest winters on record, Philadelphia could end its prolonged zero-less  streak. Single digits are looking like a sure thing.

But the official National Weather Service temperature at Philadelphia International Airport hasn't visited "the nothing that is," to borrow from poet Wallace Stevens, since Jan. 19, 1994, when President Bill Clinton was finishing up his first year in office.

This has been the second-longest wait between zero readings in the period of record, dating to the winter of 1875.

The longest interval was between Jan. 23, 1936, when it hit 2 below, and Jan. 21, 1961, -4, another noteworthy date in political local weather history. That was the morning after John F. Kennedy's inauguration, and followed a 13-inch snowstorm in Philly.

One thing we should point out is that the 1936 and 1961 Philadelphia temperatures were taken in very different environments.

In 1936, the readings were taken at the U.S. Customs House, at 2^nd and Chestnut Streets, and in 1961, at the Airport. We thank retired weather service meteorologist Jim Eberwine for providing the station list.

In 1995, the airport thermometer became part of an automated observing system and was moved to a meadow near the Delaware County border.

Being rather close to airport buildings, runways, the river, and swampland, that is a tough place to reach zero.

The official National Weather Service forecast now has the early Sunday low at 2, which is tantalizingly close to the target.

When winds are light or negligible, the presence of snow can make a huge difference in temperatures; snow allows more daytime heat to radiate into space. In addition to Jan. 21, 1961, snow was on the ground on Jan. 23, 1936.

And what are the chances that snow will be around Sunday morning? Should the snow rally later Tuesday and put down at least a few inches, it might have some staying power, despite a strengthening February sun.

Snow showers are possible Wednesday, and temperatures won't get out of the 20s the rest of the week.

Despite the cold rally, it still appears that the winter of 2015-16 is going to make it into the warm hall of fame, thanks to that otherworldly December, when the average temperature, 51.2, was 3.6 degrees above the normal temperature for November.

Only five meteorological winters – the December through February periods – had average temperatures better than 40.

This is likely to be the sixth. For that not to happen, temperatures for the rest of the month will have average better than 5.5 degrees below normal.