New numbers confirm what the sweaty brows of Northeasterners have been saying for months: The summer of 2010 was a record-breaking scorcher.
Preliminary figures provided by the Northeast Regional Climate Center at Cornell University on Friday show 28 cities from Washington, D.C., to Caribou, Maine, set record highs for average temperature from March through August.
A large swath of the country sweltered in early August, when scorching temperatures and high humidity made it feel like at least 100 degrees in many places and prompted heat advisories for 18 states. While unrelenting heat is the norm in the Deep South, it's unusual in places like Burlington, Vt., and Portland, Maine, which saw their hottest spring and summer in more than a century.
The temperatures are consistent with a global pattern of severe heat-related weather this summer. Meteorologists say 17 nations have recorded all-time-high temperatures this year, more than in any other year.
Back in the normally temperate Northeast, the records are expected to stand. The remaining days of August are forecast to be hot with readings around 90 in many areas of the Mid Atlantic and Northeast.
The average temperature for a 30-day month is calculated by adding the high and low temperatures of each day and dividing by 60.
Art DeGaetano of the Northeast Regional Climate Center in Ithaca, N.Y., said the normal average temperature for March through August in Manhattan's Central Park is 62.5 degrees, and this year it was 67.5. The previous record high was 66.3 in 1991.
For June through August, the historic average for Central Park is 73.9 degrees, and it was 77.8 this year. The previous record high was 77.3 in 1966.
In Philadelphia, the March-August average this year was 68.9 degrees, surpassing 1991's record of 67.7. At Dulles International Airport in Washington, D.C., this year's average of 68.2 beat the 1991 record of 66.4, and in Caribou, Maine, this year's spring-summer average of 54.5 degrees beat the old record of 53.5 set in 1979.
A heat wave from July 4-9 brought oppressive humidity and temperatures in the upper 90s and low 100s in many areas of the Northeast, breaking records from Maine to West Virginia.
Meteorologists caution against reading too much into the hot weather, saying such a short-term weather pattern alone cannot be interpreted as a sign of global climate change.
"Last summer was quite a bit below normal," said meteorologist Brian Edwards, of Accuweather in State College, Pa. "It's just another portion of the cycle of ups and downs that we've been going through."
"We've been under a high-pressure ridge, especially from March through late July," said meteorologist Hugh Johnson at the National Weather Service in Albany, N.Y. When the jet stream is forced northward, as it has been this summer, the region to the south of it gets high pressure with sunshine and warmer air, Johnson said.
"Last summer was the opposite," Johnson said. "We were under a trough much of the summer, making it unusually rainy and cool."
That was the case this summer in southern California, which had the chilliest July on record.
The National Climatic Data Center reported that July was the second-warmest on record worldwide, and 2010 is on track to be the hottest year.
Atmospheric scientists have grown increasingly concerned about human-induced global warming in recent years, though political pressures and fierce arguments about climate change have slowed efforts to develop solutions.