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.
As the Northeast further dries out amid another rain-free weekend, residents may be wondering if this is a sign of things to come for July.
Severe weather is threatening the north-central United States this weekend, including some areas that were hit by violent storms on Wednesday.
Showers threaten to cause delays on a nearly daily basis next week at the 2016 Wimbledon Championships.
At least 23 people have died in West Virginia as a result of extreme flooding that inundated portions of the state on Thursday.
Another round of sizzling heat threatens to aggravate the ongoing wildfire situation across the southwestern United States through early week.
Air conditioning costs U.S. homeowners nearly $11 billion in energy expenses annually, according to the U.S. Department of Energy.
Portland, OR (1925)
101 degrees -- earliest over 100 in city's history.
Anchorage, AK (1953)
86 degrees -- record high for city.
Ohio Valley, Lower Great Lakes (1988)
Extreme Heat: Location: High Temperature(F): Canton, OH 100 Erie, PA 100 Milwaukee, WI 100 Pittsburgh, PA 98 (June record) Youngstown, PA 99 (hottest so early in season) Buffalo, NY 96 Toledo, OH 104 (June record) Detroit, MI 104 (June record tied) Chicago, IL 103 Cleveland, OH 104 (all-time record) Ft. Wayne, IN 106 (all-time record tied) South Bend, IN 104 (June record) Cincinnati, OH 102 Dayton, OH 102 (June record) Evansville, IN 101 Indianapolis, IN 102 (June record tied) Lexington, KY 101