The seven-month (January-July) average of 49.9 degrees Fahrenheit was the warmest such period in 117 years, a release from the Northeast Regional Climate Center at Cornell said.
The 12-month period that ended July 31 was also the warmest such period in the Northeast in all of the states except West Virginia -- where the average temperature of 54.7 degrees missed tying the record set in 1932 by 0.1 degree, researchers said.
High temperature records were set at many of the region's recording stations during July as the mercury soared into the upper 90s and low 100s.
The sensor at Washington's National Airport recorded 105 degrees July 7, surpassing the record of 102 degrees set two years ago.
Baltimore's temperature of 104 degrees on July 18 broke the city's record of 102 degrees set in 1887, researchers said.