Despite several days of humid weather with temperatures soaring toward 90 degrees in the Roanoke and New River valleys, the air quality remains good throughout the region, according to the Department of Environmental Quality.

"So far we've been doing pretty well in the Roanoke Valley area," Virginia DEQ meteorologist Dan Salkovitz said Wednesday.

Remnants of Hurricane Dennis and Tropical Storm Cindy have brought warm and misty air into the Roanoke region.

According to DEQ, air typically swoops down from the Ohio River Valley into the region during the summer, bringing pollutants that worsen air quality. However, the tropical air coming from the south tends to clean pollutants out of the air.

"The air was clean when it moved into the Roanoke area," Salkovitz said.

The moist but clean tropical air has kept air quality in the moderate range on the Air Quality Index, which monitors air conditions based on the amount of ground-level ozone and particle pollution in the air at a given time. Salkovitz said the Roanoke area came close to reaching an orange alert, the third highest alert on the scale, earlier this month. Typically, an orange-level alert happens two to three times a year; it has yet to happen this year and didn't happen at all last summer.

An orange-level alert was issued for Richmond's air quality for today.

While temperatures have been steamy, the daytime highs have not been unusually warm in Southwest Virginia.

"We have more moisture in the air than normal," said Phillip Manuel, a meteorologist at the National Weather Service in Blacksburg. "The daytime temperatures haven't been excessive, the nighttime have."

The mass of air that has settled over the Roanoke and New River valleys has made nighttime temperatures 5 to 10 degrees above normal for the past few days, according to the weather service. Dense moisture loses heat more slowly at night, which keeps the low temperatures up.

Daytime temperatures could get hotter by the weekend, as the air mass dries some. Highs are forecast to be above 90 degrees through most of Virginia by Saturday and Sunday, with some mid- to upper-90s expected east of the Blue Ridge.

Weather columnist Kevin Myatt

contributed to this report.