The answer has to do with the air currents in the atmosphere, according to Mark Chenard, a meteorologist at the Weather Prediction Center in College Mark, Maryland. Most of the time, winds in the atmosphere flow from west to east; this is called “zonal flow” and it’s responsible for our everyday weather. But every once in a while, the winds start flowing north to south, creating a pattern called “amplified flow.”
“Cold air from north comes down south, and warm air from the south goes north,” he says. So, warm air from the Gulf of Mexico is floating upward toward those of us in the Northeast. At the same time, a cold front is making the western parts of the country much colder than usual.
Unusual warmth should linger across most of the East at least until early March. pic.twitter.com/AEWQ2HY9Ea— Eric Holthaus (@EricHolthaus) February 21, 2018
So what’s causing these patterns? Chenard says that, most of the time, it’s just normal variability in weather patterns. It’s hard to pin any one event as being caused by global warming.
Still, as Robinson Meyer at The Atlantic notes, one big sign of climate change is warmer winters. Global temperatures have been rising, and as a result, winters are warmer than they used to be. For the past three years now, Earth has been breaking its own temperature records. And ice in the Arctic is shrinking — last month, the average ice extent was the smallest on record for January.
Record-breaking temperatures on the East Coast are unlikely to last more than a day or two, says Chenard. But the pattern of “warmer than normal” days will probably last into the beginning of March, so there are a few more days to enjoy — unless climate change keeps you up at night.