(National Weather Service)

When you think of Washington, you usually don’t think about wildfires as a serious natural hazard. But, under the right conditions, dangerous wildfires can and do develop in the region, especially in open, brush-filled areas where there is dry vegetation.

The National Weather Service has issued a “red flag warning” from noon to 8 p.m. Thursday for much of the region. “A Red Flag Warning means that critical fire weather conditions are either occurring now, or will shortly,” it said. “A combination of strong winds, low relative humidity, and warm temperatures can contribute to extreme fire behavior.”

Let’s briefly examine why we’re in this situation.

The air is dry

Relative humidity values Thursday afternoon are expected to hover only in the 20-to-30-percent range. In such dry air, fires can quickly spread, and it becomes difficult to contain them.


NAM model forecast relative humidity at 2 p.m.

The ground is dry

The U.S. Drought Monitor has placed much of the region in either its “abnormally dry” or “moderate drought” categories. Three of the past four months have registered below-normal precipitation in Washington. These dry conditions remove moisture from vegetation, turning it into “fuel” that can burn quickly if ignited.


(U.S. Drought Monitor)

It’s warm

Afternoon highs in the low to mid-70s will speed up evaporation, drying the air and ground further.


Forecast high temperatures Thursday afternoon from NAM model.

It’s windy

Winds from the south this afternoon are expected to gust to 30 mph or so. Such winds can fan the flames once a fire initiates.


Forecast wind gusts at 5 p.m. Thursday.

For all of these reasons, which collectively prompted the red flag warning, the Weather Service and local emergency management officials are urging people to avoid outside burning and to properly dispose of cigarettes. If you see a fire, report it immediately.

Fire-enabling conditions are forecast to ease some on Friday because of lighter winds and somewhat higher humidity, even though air temperatures will warm to near 80.

The last time the Washington region was under a red flag warning was about a year and a half ago. In February 2011, multiple fires flared because of abnormally warm, windy and dry weather in Prince George’s and Prince William counties. In April 2016, the Rocky Mount fire charred more than 5,000 acres in Shenandoah National Park.