GRAY — The National Weather Service has issued an air quality alert for Knox and Coastal Waldo counties Thursday afternoon, with poor air quality likely to continue into the weekend up and down the Maine coast.

The air quality alert is in effect until 11 p.m. Friday, May 31.

The state Department of Environmental Protection recommends that individuals consider limiting strenuous outdoor physical activity during the alert, to reduce the risk of adverse health effects.

Those with asthma or heart disease or other pre-existing conditions, as well as the very young and the elderly, or most at risk.

The five-day forecast follows.

Thursday night: Mostly clear, with a low around 56 F. West wind around 5 mph.

Friday: Sunny, with a high near 80 F. Southwest wind 5 to 15 mph.

Friday night: Patchy fog after midnight. Otherwise, partly cloudy, with a low around 59 F. Southwest wind 5 to 10 mph.

Saturday: Mostly sunny, with a high near 80 F. Southwest wind around 5 mph.

Saturday night: A 40 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 55 F. Southwest wind 5 to 10 mph.

Sunday: A 40 percent chance of showers and thunderstorms. Partly sunny, with a high near 75 F.

Sunday night: A 50 percent chance of showers and thunderstorms. Cloudy, with a low around 57 F.

Monday: A chance of showers. Cloudy, with a high near 69 F. Chance of precipitation is 50 percent.

Monday night: A 50 percent chance of showers. Cloudy, with a low around 52 F.