If you walked outside at the right time this morning, you could see your breath — on May 8th.
So why, just when we thought we were in the clear, are we waking up seeing temperatures in the 40s and contemplating turning back on our heat?
It’s because May is the new February. Happy Groundhog Day! What generally happens in the early winter in Philadelphia is happening now.
Mitchell Gaines, a meteorologist with National Weather Service Mt. Holly, explained this latest cold spell happened because of high-pressure systems floating over Greenland and the Central Plains. He calls them “blocking patterns.” By lingering over Greenland in the North Atlantic and the middle part of the our country, cool air from Canada has nowhere to go but over the East Coast.
Usually, this kind of pattern develops for East Coast cities in February. But as you likely recall, Philly in February felt like Phoenix. Those high pressure blocking patterns weren’t there, allowing southern winds to inundate the East Coast.
Why the switch now? Gaines said these high-pressure systems occur because of the North Atlantic Oscillation, which is basically a constant, massive storm that wreaks havoc on weather patterns throughout the Northern Hemisphere. And after a long delay, it’s getting stronger.
“It’s kind of just flipping the switch,” Gaines said, “and heading into the pattern that we are in now.”
That pattern entails May being about 10-to-15 degrees colder than average for the next week or so. So far this month, Philly has had three days over 70 degrees. It’s not expected to get back above 70 until mid-May. In February, Philly had four days of 70-plus temperatures and two days of 65-plus.
March, which had a colder average temperature than February and that really annoying snowstorm, had two days of 70-degree weather. April had 10.
These schizophrenic patterns are unusual but not unprecedented. Gaines said Philly saw warm winters with freakish cold later on in the spring in 1983 and 1984.
Those blocking patterns should dissolve in the next couple weeks and not ruin our summer. It’s just going to feel like February for a little while longer.