A heat advisory issued by the National Weather Service in Wilmington has been extended through Saturday.

Hamilton, Clermont, Butler and Warren counties in Ohio are under the watch, as well as Campbell, Kenton, and Boone counties in Kentucky and Dearborn, Franklin, Switzerland, and Ohio counties in Indiana.

According to the National Weather Service, expect a prolonged period of dangerously hot conditions with heat index values around 100 degrees. Highs in the lower to mid-90s will be compounded by low temperatures in the 70s, leading to a warm and muggy night.

Friday’s highs will hit the mid-90s, with afternoon dewpoints generally in the mid- to upper 60s. This will lead to heat index values just two to three degrees above actual air temperatures.

Hot and humid conditions will continue through Sunday until a cold front moves through the region, bringing brief relief from the heat.

The weather service advises that individuals take extra precautions outside as hot temperatures and high humidity may cause heat-related illnesses. Wear lightweight, loose-fitting clothing and limit strenuous activities to the early morning and evening. Also, drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors.

Take action if you start to see symptoms of heat exhaustion and heat stroke.

The Southwest Ohio Air Quality Agency has also issued an air quality alert through Thursday night.

The alert covers Butler, Clermont, Clinton, Hamilton, and Warren counties in Ohio, Boone, Campbell, and Kenton counties in Kentucky, and Dearborn County in Indiana.

According to the National Air Quality Index, ozone pollutants are expected to reach 110 in the “orange” level. This level is considered unhealthy for sensitive groups, particularly young children, the elderly, and those with respiratory conditions.

The public is encouraged to limit outdoor exertion, especially sensitive groups.

What should you do during an air quality alert?

• Take the bus, carpool, or walk instead of driving.

• Refuel your vehicle after 6 p.m. Do not top off while refueling, and tighten the gas cap.

• Do not idle your vehicle.

• Combine trips or eliminate unnecessary trips.

• Keep your vehicle maintained with properly inflated tires and timely oil changes.

• Avoid the use of gasoline-powered equipment.

• Avoid the use of oil-based paints and stains.

• Never burn leaves or other yard trimmings.

• Burn clean, seasoned wood in outdoor fire pits, fireplaces, and wooden stoves.

• Avoid using fire pits or fireplaces for nonessential home heating.

• Conserve electricity.

Detailed 7-day weather forecast for Cincinnati

Thursday: Patchy fog before 9 a.m. Otherwise, it will be mostly sunny, with a high near 96. Heat index values as high as 102. Calm wind.

Thursday night: Partly cloudy, with a low around 74. Calm wind.

Friday: Patchy fog before 8 a.m. Otherwise, mostly sunny and hot, with a high near 98. Heat index values as high as 102. Calm wind.

Friday night: Mostly clear, with a low around 73. Calm wind.

Saturday: Sunny and hot, with a high near 99. Calm wind becoming southwest around 6 mph in the afternoon.

Saturday night: Partly cloudy, with a low around 77.

Sunday: A chance of showers and thunderstorms after 2 p.m. Partly sunny, with a high near 95. The chance of precipitation is 30%.

Monday: Sunny, with a high near 92.

Tuesday: Sunny, with a high near 95.

Wednesday: There is a chance of showers and thunderstorms. Mostly sunny, with a high near 95. The chance of precipitation is 40%.

Source: National Weather Service at Wilmington.

This article originally appeared on Cincinnati Enquirer: Weather: NWS extends heat advisory; air quality alert issued