Heat Brings Air Quality Alert For DC, Northern VA On June 28

WASHINGTON, DC — Authorities have declared an air quality alert of "orange" for the Washington, D.C. region on Friday, June 28, because of elevated ozone levels as the heat and humidity bake the area. An orange alert means "unhealthy for sensitive groups," according to the Environmental Protection Agency.

Temperatures will continue to rise today, topping out in the low to middle 90s. Combined with the humidity, it will feel like the middle to upper 90s for most, said the National Weather Service.

During the heat you should:

• Drink more fluids, regardless of your activity level. Do not drink liquids that contain alcohol or large amounts of sugar, which cause you to lose more body fluid.
• Stay indoors and, if at all possible, stay in an air-conditioned place. If your home does not have air-conditioning, go to an air-conditioned public place.
• Wear lightweight, light-colored, loose-fitting clothing.
• NEVER leave any person or animal in a closed, parked vehicle.

Check regularly on:

• Infants and young children
• Those aged 65 or older
• Those who have a mental illness
• Those who are physically ill, especially with heart disease or high blood pressure

"Think of the AQI as a yardstick that runs from 0 to 500," the EPA says on its website. "The higher the AQI value, the greater the level of air pollution and the greater the health concern. For example, an AQI value of 50 represents good air quality with little potential to affect public health, while an AQI value over 300 represents hazardous air quality. ... When AQI values are above 100, air quality is considered to be unhealthy-at first for certain sensitive groups of people, then for everyone as AQI values get higher."

Orange level would put the air quality between 101 and 150.

The Air Quality Index (AQI) is based on five criteria pollutants that are regulated under the Clean Air Act: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide and nitrogen dioxide.

Those who have sensitive medical conditions are encouraged to stay indoors.

Although general public is not likely to be affected at this level, people with lung disease, older adults and children are at a greater risk from exposure to ozone, whereas persons with heart and lung disease, older adults and children are at greater risk from the presence of particles in the air.

The air quality index drops to moderate pollution on Saturday, June 29, when air quality may pose a moderate health risk, especially for those who are unusually sensitive to air pollution.

Winds will turn southerly Monday as high pressure slides off the Mid-Atlantic coast. ... Good air quality is expected to continue thanks to a very clean residual air mass and increased afternoon cloudiness, says the Metropolitan Washington Council of Governments in its alert.

Here's the weekend forecast for DC and northern Virginia from the National Weather Service:

Friday: Scattered showers and thunderstorms, mainly after 3pm. Partly sunny, with a high near 93. Light and variable wind becoming southwest 5 to 7 mph in the afternoon. Chance of precipitation is 30%.

Friday Night: Scattered showers and thunderstorms, mainly before 9pm. Mostly cloudy, with a low around 75. South wind around 5 mph becoming calm after midnight. Chance of precipitation is 40%.

Saturday: A slight chance of showers and thunderstorms after 2pm. Mostly sunny, with a high near 96. West wind 5 to 10 mph. Chance of precipitation is 20%.

Saturday Night: A chance of showers and thunderstorms, mainly before 11pm. Mostly cloudy, with a low around 76. West wind 6 to 9 mph. Chance of precipitation is 30%.

Sunday: A slight chance of showers between 8am and 2pm, then a slight chance of showers and thunderstorms after 2pm. Mostly sunny, with a high near 92. Northwest wind 9 to 14 mph, with gusts as high as 23 mph. Chance of precipitation is 20%.

Sunday Night: Mostly clear, with a low around 70.