January 2014 will go down as the month we all learned about the polar vortex (even if meteorologists have known about it for decades). It’s the month when it got so cold that Minnesota closed all schools for the first time since 1997, when much of the Midwest was more frigid than the North Pole, when even Tampa experienced temperatures below freezing. As I write, much of the eastern half of the country is suffering through another bitter cold snap—not caused by the vortex, FYI—one that has blanked the East Coast in heavy snow. Winter, in short, has felt miserable.
But here’s the surprise: on a historical and national level, it hasn’t actually been all that cold. With data from Weather Underground, I calculated the average high daily temperature from Jan. 1 through Jan. 22 for the 10 largest cities in the U.S. The results make this winter look surprisingly average:
Jan. 2014 Average High Historical Average High
New York: 38 F (3.3 C) 36 F (2.2 C)
Los Angeles: 76 F (24.4 C) 68 F (20 C)
Chicago: 27 F (-2.7 C) 32 F (0 C)
Houston: 64 F (17.8 C) 63 F (17.2 C)
Philadelphia: 40 F (4.4 C) 41 F (5 C)
Phoenix: 73 F (22. 8 C) 67 F (19.4 C)
San Antonio: 66 F (18.9 C) 63 F (17.2 C)
San Diego: 72 F (22.2 C) 65 F (18.3 C)
Dallas: 58 F (14.4 C) 57 F (13.9 C)
San Jose: 66 F (18.9 C) 58 F (14.4 C)
What do we learn from this? Well for one thing, there’s an East Coast bias in news coverage, at least of the weather. But while it truly has been historically cold on average for much of the Midwest, for most of the rest of the country the average temperatures have been around normal, or even a little above. And the West Coast is experiencing an unusually hot winter (one that has compounded the record drought in California). Average high temperatures have been further above normal in Los Angeles and San Jose than they’ve been below average in Chicago. Anchorage has been positively balmy—by Alaskan standards—with average daily highs that are 11 F (6.1 C) greater than the historical average for January.
So why has this month felt so unusually cold for so many Americans? Probably because it has been—at least compared to recent history. An Associated Press analysis found that from 1900 on, cold extremes happened about once every four years. But when the average temperature in the U.S. dropped below 18 F on Jan. 6, it was the first time the country had been that cold on average in 17 years. And that day was only the 55th coldest day in recorded U.S. history, much warmer than the 12 F average recorded on Christmas Eve 1983.
The climate has been changing, but so have we, adjusting to what you might call a new normal. It’s an example of “shifting baselines,” a term first coined by the fisheries scientist Daniel Pauly. Once a New York City January when high temperatures were 38 F on average would have seemed on the warmish side. But as the climate has changed—and it has, with winters in New York State more than 1 F warmer on average now than in 1970—so have our perceptions of what’s normal. So when we get a winter that would have been pretty average four decades ago, it feels like a deep freeze.
And who knows, by 2100—when average temperatures in the U.S. might be as much as 11 F higher if nothing is done to slow greenhouse gas emissions—our descendants might even get a freak January in New York when average temperatures actually fall below 40 F. And they’ll call it a cold snap.