As intense heat continues to move across the eastern two-thirds of the nation throughout the week, air quality will likely suffer as a result.
The cities plagued most by the heat will be St. Louis, Kansas City, Chicago, D.C. and Philadelphia.
Air quality will deteriorate in these areas, with most of the East and Midwest facing moderate health concern as a result of the air quality.
According to the air quality index at airnow.gov, a moderate health concern means that 'air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.'
Areas of more serious concern include Atlanta, Pittsburgh, St. Louis, Chicago, Detroit, Cleveland and Cincinnati.
These areas have been temporarily deemed unhealthy for particularly sensitive groups. According to airnow.gov, "Members of sensitive group may experience health effects."
The general public is not likely to be affected, the site explains.
It's not a coincidence that poor air quality usually accompanies heat waves.
"When you get a large area of high pressure promoting widespread heat, you also get a large zone of stagnant air," said AccuWeather.com Meteorologist Meghan Evans.
"Smoke and ozone can be trapped in the atmosphere, leading to poor air quality."
For the full story on the heat, click here.
Some cooler weather is in store for Chicago this week as thunderstorms roll into the area around late week.
A dangerous multiple-day severe weather outbreak will begin this weekend over the South Central states and will include the potential for nighttime tornadoes in parts of Texas and Kansas.
A large storm will form over the eastern half of the nation next week and will bring a swath of unsettled conditions for days.
Stormy weather will continue in the Dallas area through Thursday morning, but conditions will improve on Friday.
A slow-moving low pressure system will make residents of the Northwest reach for their raincoats and umbrellas each day through the remainder of the week.
Surviving a flight in the wheel well of a commercial aircraft is possible, but highly unlikely due to subzero temperatures and thinner air than what is found at the peak of Mount Everest.
Caldwell, TX (1990)
13.4" of rain in the span of 3 hours.
Baltimore, MD (1991)
Hail 1-1/2" in diameter fell north of Baltimore City.
Mauna Kea & Mauna Lea, HI (1995)
6" of snow above 13,500 feet.