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.
The wet weather pattern across the Seattle area will continue through the week, creating poor travel conditions in the region ahead of Christmas Eve and Christmas Day.
Soggy weather will be the rule in the run-up to Christmas in the Atlanta area.
Holiday travel will be at risk across the Harrisburg area this week as a strong storm takes shape and blasts through the Northeast.
Holiday travel will be at risk across the Pittsburgh area this week as a strong storm takes shape and blasts through the Northeast.
After a few mild days at the start of the week, temperatures will fall in time to create some wintry weather and travel woes for Christmas.
After a few mild days at the start of this week, temperatures will fall in time to create some wintry weather and travel woes for Christmas.
Portland, MI (2001)
34 consecutive days with measurable rainfall.
Second of triple December storms - 25" at Gettysburg, PA.
Kansas City (1961)
16.6" snow, greatest in December.