Connecticut logged nearly twice the number of unhealthy air days this past summer as it did the summer before, the U.S. Environmental Protection Agency reported Tuesday.

The EPA and the State Department of Environmental Protection said this summer’s hot temperatures are to blame for much of the increase, because hot weather aggravates pollution emitted from cars and industry.

Last summer was much cooler, resulting in fewer bad air days.

The EPA monitors ground-level ozone in the air. Ground-level ozone, the main ingredient in smog, can seriously sicken the elderly and people with breathing problems.

Connecticut had 25 days of unhealthy air this summer, compared to 13 last year. Massachusetts had 27 unhealthy air days, compared with five last year, and Rhode Island had 15, compared with eight last year.

Each day’s air was considered unhealthy if monitors detected ground level ozone at .08 parts per million or greater over an eight-hour period.

Despite the increase in unhealthy air days this year, the EPA said the air overall is getting cleaner in New England.

Air pollution data was collected from May to the end of September.

–Associated Press