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.
Hurricane Ignacio may enhance showers and stir rough surf for the Hawaiian Islands as it approaches next week.
After Erika brings heavy rain and locally gusty winds from Hispaniola eastern Cuba into Friday night, the system will move toward the Bahamas, the Keys and South Florida this weekend.
As many as seven tropical cyclones were churning throughout the world this past week, while smoke from wildfires across the Pacific Northwest led to poor air quality across the region.
Heat and humidity will return to Harrisburg this weekend and hang on into next week.
Heat will linger in Eastern Europe for much of the fall season; meanwhile, the British Isles and northwestern Europe can expect a stormy end to the season.
As Hurricane Katrina barreled towards the Gulf Coast, peaking at Category 5 strength while feasting on the warm waters of the Gulf of Mexico, meteorologists around the country prepared to deliver one of the most crucial and life-saving forecasts in history.
Sherman Pass, WA (1980)
2 inches of snow.
Pennsylvania & New Jersey (1971)
Tropical Storm Doria caused severe floods in southeastern PA and NJ. Damage estimated at $138 million.
Colorado Springs, CO (1978)
Hail 6 inches deep.