Warm December: Why winter temps are high in Philly, and how long this will last

Enjoy it while you can, though; El Niño’s glorious effect won’t last forever.

Warm weather

Since Thanksgiving, Philadelphia has entered a state of meteorologic bliss that has made our city’s weather comparable to Southern California. The temperatures have mostly crept above 50 and the sun has been out at a time when the average is somewhere in the mid-40s and gray clouds often rule.

This weekend it gets better. The highs are supposed to top 60 every day. And for this good fortune, we have El Niño and the right mix of jet streams to thank.

Sarah Johnson, a meteorologist with the National Weather Service in Mt. Holly, said those factors are causing low pressure systems to stay where they belong: Up north in Canada, rather than heading south and freezing us, like they would normally this time of year. Low pressure systems bring rain and cold. Without those low pressure systems mucking things up, Johnson said Philadelphia has been getting a  “Southernly flow” that has let us walk around without heavy coats.   

A comparison to So Cal is no joke. Los Angeles’ highs the next five days, according to Accuweather, are 64 for today and then 67, 67, 60 and 61. Philly has 65 for today then 66, 67, 66 and 59. This December, the recorded high hasn’t been below 50 even once, and the low has hit the freezing point just once.

Still, this isn’t the warmest Philly December in modern history. The four consecutive days we’re predicted to have over 60 degrees is unusual but not unprecedented. In 1998, according the National Weather Service, Philadelphia experienced seven straight days of 60-degree and up temps. Two of those days went above 70. Just two years ago, temps went above 60 four times in December but not on consecutive days.

Johnson said the sun and above-average temperatures should continue through the rest of the month, with possibly a few dips into the average or below average. But enjoy it while you can. El Niño’s glorious effect won’t last forever.

“For our region it means that winters start off warmer,” Johnson said. “It doesn’t mean it’s going to stay that way through the winter.”

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