The dense fog conditions that started the day and then dissipated have returned, with the National Weather Service issuing a dense fog advisory in effect for Long Island through 1 a.m. Tuesday.

That means possible visibilities of a quarter mile or less, so drivers are advised to slow down, use high beams and leave plenty of room ahead in case they must stop suddenly, the weather service said.

The conditions have also led to delays at Kennedy, LaGuardia and Long Island MacArthur airports, according to the Federal Aviation Administration website, with the FAA advising travelers to check with their airlines.

Light rain could be starting after 8 p.m. Monday, with chances of it picking up in the 11 p.m. to 1 a.m. time range, said Joe Pollina, weather service meteorologist based in Upton. Around a quarter to a half inch is in the forecast.

Apart from all that, Long Islanders continue to enjoy unusually warm temperatures for December, with the record of 58 degrees in 2001 tied with Monday’s high at MacArthur Airport.

If 59 degrees had been reached, it would have marked the fifth day in a row of record highs, with this past weekend delivering back-to-back record-breaking highs of 68 degrees, preceded by Friday’s 59 and Thursday’s 61 at Long Island MacArthur Airport.

advertisement | advertise on newsday

As of day’s end Sunday, the airport was averaging 9.4 degrees above normal for the month.

Interestingly, that earns the airport just the second-warmest title for the first 13 days of December, with 1998’s average temperature of 48.1 degrees surpassing this year’s 47.7, according to data from the Northeast Regional Climate Center based at Cornell University.

And we are still a distance away from beating the record for warmest day ever in December, at least since records at the airport started being kept 30 years ago. That “scorcher” was 77, seen Dec. 7, 1998.

@Newsday

So, what’s behind these balmy conditions that are more April- than December-like?

“The polar jet stream continues to stay well to our north, allowing warm southern air to bring above normal temperatures to the Northeast,” said Jessica Spaccio, climatologist with the center.

The forecast for Tuesday is for highs around 60, which could surpass 2008’s daily record of 59 in 2008.

Don’t get too attached, though, to these light-jacket days. Rich Hoffman, News 12 Long Island meteorologist says that, “one cold front tonight [Monday] will bring cooler weather in for Wednesday and another cold front on Thursday brings colder weather for the weekend.”

And, just as a reminder — normal highs for this time of year are around the mid-40s.