Portland experienced its hottest August on record this year, driven primarily by high humidity that prevented the mercury from falling overnight.

Portland also tied the record set in 2016 for warmest meteorological summer, which is June 1 through Aug. 31, according to the National Weather Service office in Gray.

The average temperature in August was 72.2 degrees, which is 4.2 degrees above normal, said weather service meteorologist Chris Kimble. The previous record for August was 71.8 degrees, set in 2016, he said.

A man sleeps on a beach chair in the shade of an umbrella at Old Orchard Beach during another day of hot weather.

“We set the record for the warmest August on record in Portland,” Kimble said. “That was driven primarily by the low temperatures, which were even more above normal (than the highs).”

Abnormally high humidity was the primary reason temperatures did not fall as much as they usually do at night, he said.

There were seven days in August in which the low temperature remained above 70 degrees, Kimble said, the most ever recorded for the month. There were five days in August in which the low temperature for the day set or tied the record for warmest ever.

Only one record high temperature was achieved in August: 93 degrees on Tuesday, which tied the record for Aug. 28 set in 2001, he said. The all-time record high temperature for August in Portland was 103 degrees, set on Aug. 2, 1975.

The average high temperature in August this year was 80.8 degrees, compared with the historical average of 77.7 degrees, and the average low temperature was 63.5 degrees, compared with the historical average of 58.2 degrees.

“For eight straight days, from Aug. 2 to 9, Portland did not drop below 65 degrees, including five days straight that did not drop below 70,” Kimble said. “There were a few breaks in the middle of the month when cold fronts brought some cooler air and occasional rainfall, but the heat and humidity returned before the month was out.”

Portland also tied the record for warmest meteorological summer set in 2016, with an average temperature of 68.9 degrees, Kimble said. The average temperature for the three-month period was 2 degrees above normal, he said.