More than 350 sites across a broad swath of the continent's interior have posted daily record highs since June 27, with heat advisories on Friday covering all or parts of 23 states from Kansas east to the Carolinas and into the Northeast, and from Wisconsin south to Mississippi and Alabama.
At the same time, other parts of the country are reporting record lows for this time of year.
Anyone looking for relief might put the Northwest on their itinerary. Over the same two-day period, 57 locations, largely clustered in Washington state and northeastern Oregon, posted at least one daily high temperature that tied or beat the lowest for the date on which it was measured. Waterville, Wash., posted the biggest drop among the group – a high of 51 degrees on Wednesday, nine degrees below the previous record-low high of 60 degrees on June 27, 1946.
And it's all coming out of a spring that was the warmest on record in the US, bringing a heat wave to the center of the country in March the likes of which the US hasn't seen since 1910. Indeed, Spring 2012 in the US was 2 degrees warmer than the previous record-holder, the spring of 1910.
One reason for the seemingly relentless high temperatures is the presence of a broad ridge of high pressure inching its way across the continent, forecasters say. With skies generally clear, sunlight has a clear path to travel on its way to baking what in many places is an already parched surface.