PORTLAND – Maine and New England experienced fewer smoggy days this summer than in 2002 because of cool temperatures, the Environmental Protection Agency reported Wednesday.

In Maine, the number of high-ozone days – days when the smog creates unhealthy conditions by federal standards – fell to just five this year, down from 17 last year. The ozone season runs from May through September.

The number of smoggy days fell sharply in all New England states this summer. Vermont did not have a single day when ozone levels reached unhealthy levels.

Robert Varney, regional administrator of the EPA’s New England office in Boston, said the number of smoggy days in the region has decreased significantly over the decades. The peak year in the past 20 years in Maine came in 1988, when the state experienced 35 days with unhealthy ozone levels.

Varney said more needs to be done to reduce the numbers even more. Smog has numerous sources, including cars, trucks, power plants and even gasoline-powered lawn mowers, and is made worse by sunlight and high temperatures.

“When we look back to the air-quality conditions a generation ago, we can feel proud of the advances we’ve made in reducing pollution,” Varney said. “The fact that we still see unhealthy days during cool summers, however, reminds us that our efforts for cleaner cars and fuels and our commitment to reducing power plant emissions must continue.”

Around New England, New Hampshire had one high-ozone day this summer, down from five last year, and Massachusetts had 11 such days, down from 30. Rhode Island had 10 smoggy days this summer, a decline from 17 in 2002. Connecticut recorded 14 high-ozone days this year compared with 36 in 2002.