The past 12 months in the contiguous U.S. were the warmest since records began in 1895, according to a report released by the National Oceanic and Atmospheric Administration Monday.
July 2011 through June 2012 only narrowly surpassed the record broken last month for the June 2011 through May 2012 period by 0.5 degrees F.
The January 2012 through June 2012 period was the warmest first half of any year on record for the contiguous United States with the national temperature of 52.9 degrees, placing 4.5 degrees F above average.
Though cooler-than-average temperatures were present for the Pacific Northwest and for the beginning half of June in the Southeast, the latter half of June spurred record-breaking temperatures across a large portion of the nation.
Over 170 all-time warm temperature records were broken or tied during the month of June.
AccuWeather Expert Senior Meteorologist Jack Boston believes the dry and mild winter created the warmer-than-normal spring and warmer summer.
"We had a progressive weather pattern during the winter time. The air masses that came across the U.S. came from the west; they were pacific air masses. All the arctic air was cut off. That led to the unusually mild winter," Boston said.
"It was also a very dry winter, so the dryness of the winter helped it stay warm through the spring and into the early summer. The sun was able to more efficiently heat the surface because the surface wasn't wet," he said.
In addition to the heat, drought plagued nation in June.
As of July 3, 56.0 percent of the contiguous U.S. experienced drought conditions, marking the largest percentage of the nation experiencing drought conditions in the 12-year record of the U.S. Drought Monitor, the report reads.
The heat and the drought are related," Boston said.
"Drought conditions and higher-than-normal temperatures feed each other. Sun heats dry surface more efficiently, as all energy goes to heating and not evaporation."
For the full report from NOAA, click here.
On this week's edition of AccuWeather LIVE, we'll take a look at an upcoming winter storm and how it may affect holiday travel.
Big changes are on the way for parts of the Western and Central states late this week and into this weekend.
Warm air is forecast to surge into much of the eastern half of the nation by the weekend and will be accompanied by heavy rain and flooding risk in some locations.
Thunderstorms in parts of the South this weekend may become strong enough to threaten lives and property.
As record-challenging warmth air pays a brief visit to the Eastern states, delays from rain, fog, ice and snow will be on the increase this weekend over much of the nation for early holiday travelers.
Tune in weekdays at 7 a.m. EST for the latest edition of AccuWeather LIVE.
Philadelphia, PA (1991)
High of 30 degrees; only 5th day in 1991 with a high below freezing.
Flagstaff, AZ (1967)
End of record 7-day snowstorm; total 83" snow.
Riverside RS (Yellowstone Park), WY: -59 degrees, lowest U.S. temp in December.