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It’s a sizzler. Boston is in the midst of its second heat wave of the month.

The temperature at Boston’s Logan International Airport reached 96 by 2:30 p.m. Tuesday, according to the National Weather Service. That followed high temperatures of 93 there on both Sunday and Monday.

An official heat wave is three days of temperatures of 90 degrees or more.

Another three-day stretch of the month, July 19 through July 21, featured high temperatures of 93, 97, and 98.

But the month has been blazing hot generally, with 11 days, including Tuesday, where the temperature reached 90 or more, according to the weather service.

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A heat advisory remains in effect until 8 p.m. owing to “a situation in which heat illnesses are possible,” forecasters said.

The public can also expect some unhealthy air in parts of Massachusetts on Tuesday, officials said.

Via Twitter Monday, the state Department of Environmental Protection sounded the alarm.

“#AirQualityAlert: Unhealthy #air quality for sensitive groups expected in #MA tomorrow from 11am-11pm in #Hampden, #Hampshire, #Franklin, Southern #Berkshire & #Essex counties,” the department tweeted.

A DEP online map showed the air at “moderate” quality in parts of central and southeastern Mass. on Tuesday.

Here’s what moderate means:

“Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people,” the DEP says on its website. “Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors.”

The general takeaway for the hot weather? Take it slow.

“The combination of hot temperatures and high humidity will combine to create a situation in which heat illnesses are possible,” the weather service said. “Drink plenty of fluids, stay in an air-conditioned room, stay out of the sunshine, and check up on relatives and neighbors.”

Forecasters also provided safety tips for performing outdoor work in the stifling heat.

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“To reduce risk during outdoor work, the Occupational Safety and Health Administration recommends scheduling frequent rest breaks in shaded or air conditioned environments,” the weather service said. “Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency, call 911.”

Tuesday’s advisory came after the weather service’s announcement Monday that a third tornado had touched down on Cape Cod during last week’s storm that rocked the region, felling trees and power lines, and even tearing the roof of a Yarmouth motel.


Travis Andersen can be reached at travis.andersen@globe.com. Follow him on Twitter @TAGlobe.