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.
Rounds of drenching showers and heavy thunderstorms will heighten the risk of flash flooding across the northeastern United States through the final weekend of July.
Tropical Storm Nida threatens to bring flooding rain to the Philippines into this weekend with future impacts on China and Taiwan.
As several large fires continue to rage across the western United States, weather conditions will gradually improve for firefighting efforts in the upcoming week.
Additional downpours are likely to roll across northern New Jersey and further suspend play during the late rounds at the 98th PGA Championship at Baltusrol Golf Club this weekend.
A tropical wave approaching the Caribbean Sea will attempt to reactivate the Atlantic Basin during the first week of August.
A hot air balloon carrying at least 16 people crashed in central Texas on Saturday morning. Authorities say there appears to be no survivors.
Las Vegas, NV (1998)
2.50 inches of rain in 1 hour.
Greenville, SC (2004)
Heavy rain causes nearby river to crest at 19.2 feet, the second highest crest ever.
"A considerable flood arose unexpectedly which proved detrimental to many in that colony." This was the first of 2 hurricane/floods within 30 days.