Washington DC’s air quality has worsened this week as wildfire smoke from Canada traveled hundreds of miles south, prompting air quality alerts and creating hazy skies across the region.

There’s belief by some forecasters that the worst is yet to come.

Here’s what they say about Friday’s forecast, which Capital Weather says could feature “the worst air quality in years” in DC.

Could air quality reach Code Red levels in Washington DC?

Washington DC’s air quality reached Code Orange this week, meaning conditions are unhealthy for sensitive groups, including children, older adults and people with heart or lung disease.

Forecasters warn conditions could deteriorate further Friday as a thicker plume of wildfire smoke settles over the region. The Maryland Department of the Environment’s forecast suggests parts of the DC metro area could reach Code Red — an AQI of 151 to 200 — if the heaviest smoke reaches the surface.

“A weak cold front will move south Thursday night and Friday morning, ushering in a significant amount of smoke into Maryland that will persist all day Friday due to weak, recirculating winds,” officials said.

Capital Weather Gang reported that smoke concentrations are expected to peak Friday afternoon into Friday evening, when air quality could deteriorate to levels not seen in three years.

Other forecasters indicate the highest concentrations of smoke are expected late Friday before conditions gradually improve over the weekend.

What do Code Red air quality levels mean?

Many areas north of DC are already in a Code Red, meaning anyone could experience health effects from the air quality, not just sensitive groups.

On the Air Quality Index (AQI) scale, Code Red represents levels between 151 and 200. At those levels, even healthy people may experience eye or throat irritation, coughing or difficulty breathing after prolonged exposure.

If the DC area were to reach that level, residents should limit their time outdoors. If you must spend an extended period outdoors, DC Health recommends wearing a well-fitting N95 or KN95 mask.

People with asthma, heart disease or other respiratory conditions, as well as children, older adults and pregnant people, may be especially vulnerable to wildfire smoke and should take extra precautions. Anyone who develops symptoms such as coughing, shortness of breath, chest pain or difficulty breathing should move indoors and seek medical attention if symptoms become severe.