June 29 has been the lone day this summer with a code red air quality alert.
June 29 has been the lone day this summer with a code red air quality alert. (AirNow)

Despite it being one of the hottest summers on record in Baltimore, "code red" air pollution days are at their lowest levels since 2009.

There has been only one "code red" day, considered unhealthy for everyone -- June 29, the day intense heat fueled the deadly derecho storm. That is according to AirNow, an air-quality website maintained by a handful of federal government agencies.


There have been 14 days with "code orange" conditions in at least part of the Baltimore area so far this summer. On those days, air pollution can irritate sensitive populations like the elderly, young children and those with breathing difficulty.

Those are the lowest tallies since three years ago, when one code red day and eight code orange days were recorded, according to Air Quality Index archives kept by the Maryland Department of the Environment. Last year, there were five code red days and 17 code orange days.

Of course, this year's tally could rise, with about three weeks left in the meteorological summer.

High heat can contribute to smog, particularly when air is also stagnant.

There have been 39 days with temperatures in the 90s and 100s so far this year, while there are 30 such days, on average, across a full year.

July's average temperature of 81.4 degrees at BWI Marshall was the fifth-warmest since 1871, and it was an 18th consecutive month of above-normal temperatures in Baltimore.

Average wind speeds this summer have been about 5 mph, compared with speeds closer to 7 mph during the spring.

The improvement in air quality comes after the National Weather Service office in Sterling, Va., changed its policy on air quality alerts. The office, which covers the Baltimore area, no longer issues air quality alerts for code orange days -- only for code red -- as of June 5.

Have a weather question? E-mail me at sdance@baltsun.com or tweet to @MdWeather.