By Joseph O'Leary

(Reuters) - The first seven months of this year have been the hottest on record in the northeastern United States, researchers at Cornell University said on Tuesday.

Cornell's Northeast Regional Climate Center said the average temperature for the region from January to July was a balmy 49.9 degrees Fahrenheit (9.9 Celsius), making it the warmest for the period since record-keeping began in 1895.

On a state-by-state basis, the seven-month period marked the warmest across New York, New Jersey, Delaware and Maryland, along with Connecticut, New Hampshire, Maine, Massachusetts, Rhode Island and Vermont, the Regional Climate Center said.

In Pennsylvania and West Virginia, it was the second-warmest first seven months of a year.

The 12 months that ended July 31 were the warmest in 117 years in every northeastern state expect West Virginia, the university researchers said.

"We're seeing quite a bit of these records being broken in the 2000s," said Mark Wysocki, a senior climatologist at the Northeast Regional Climate Center, adding that four of the top 10 highest averages were set during the past 12 years.

Heat waves, coupled with droughts and wildfires, have grabbed headlines across much of the United States this year.

But many scientists have cautioned against reading too much into a relatively small set of data or saying whether the extreme weather events are unmistakable evidence of global climate change.

(Editing By Joseph O'Leary and Cynthia Osterman)