Minimum temperature rankings for January-July, 2014. Red is record warmest, dark blue record coolest. Climate.gov

In the U.S., we're living in two countries: one scourged by heat and the other bitten by cold.

This year is shaping up to be one of the weirder ones in America's weather history. That's because we now seem to be living in two geographically separate nations: one scalded by unbearable heat, the other bitten by waves of unusual cold.

In a typical year, the U.S. has either mostly warm or mostly cool temperature extremes (meaning values at the top or bottom of a historical range of temperatures). For instance, years in the late '70s were marked by extreme cold throughout the country, while the 2000s featured increasingly frequent baths of abnormally hot weather, as pictured in this NOAA graph of January-to-July daytime highs:

(Climate.gov)

But as seen at the graph's far right, 2014 is ushering in a prominent and record-setting split between competing regions of hot and cool temperatures—the former in the drought-plagued West and Alaska, the latter in the Midwest and Missouri Valley. Climate.gov writes:

In most years in the record, extremes are significantly lopsided: A given year’s bar is mostly red or mostly blue, sometimes capped with a small segment of the opposite color. In other words, either some part of the country is experiencing warm extremes or cold extremes, but not both. Only a handful of years have a pattern similar to 2014—in which more than 10 percent of the country was experiencing extreme warmth while a similarly large or larger area experienced extreme coolness....

Even among these years, 2014 is unprecedented: Never before has the country experienced such large areas of simultaneous, opposing temperature extremes in the same January-July period. At a combined 40 percent of the country, the area affected by extremes so far this year is nearly double the size you’d expect due to chance.

If random weather patterns aren't behind the great hot/cold split, what might be? The government folks behind this latest analysis promise to post possible answers soon, but one theory comes from international scientists who published a study this spring on the history of the jet stream. They believe that the stream is locked in a "positive" phase, meaning it's hauling warmth up to the West and then blasting the East with polar chill. As the climate continues to warm, these stream-derived temperature differences could become entrenched, the scientists say, with the West experiencing more "mild, relatively warm winters" and the East increasingly winding up underneath a "freight car of arctic air."

About the Author

Most Popular

  1. Transportation

    How Seattle Bucked a National Trend and Got More People to Ride the Bus

    Three experts in three very different positions weigh in on their city’s ridership success.

  2. Equity

    The Side Pittsburgh Doesn't Want You to See

    Pittsburgh filmmaker Chris Ivey has spent over twelve years documenting the lives of the people displaced so that the city can achieve its “cool” status.  

  3. Construction workers build affordable housing units.
    Equity

    Why Is 'Affordable' Housing So Expensive to Build?

    As costs keep rising, it’s becoming harder and harder for governments to subsidize projects like they’ve done in the past.

  4. Design

    Experimental City: The Sci-Fi Utopia That Never Was

    With solar energy, recycling, computers, and personal mass transit, the 1960s-era Minnesota Experimental City was a prescient and hopeful vision of the urban future. A new documentary tells its story.

  5. People use leaning bars at a bus stop in Brooklyn in 2016.
    Design

    Cities Take Both Sides in the 'War on Sitting'

    Cities are removing benches in an effort to counter vagrancy and crime—at the same time that they’re adding them to make the public realm more age-friendly.