The National Weather Service announce has announced an excessive heat advisory is in effect for Southern Maryland until 6 p.m. Thursday.

The heat value indexes may exceed 110 degrees or higher, when calculated with the high humidity level.

Little relief is expected during the night time hours, when the heat index is expected to stay near 90 degrees.

An excessive heat advisory means that a prolonged period of dangerously hot temperatures will occur. The combination of hot temperatures and high humidity will combine to create a dangerous situation in which heat illnesses and fatalities are likely.

The National Weather Service issued the following precautions:

1. Drink plenty of fluids. Wear light colored clothing and a hat.
2. Plan to spend afternoons in an air conditioned room.
3. Plan any outdoor activities for the early morning hours.
4. Check up on elderly family and neighbors-these people are at the most risk.
5. Provide outside pets and livestock with plenty of water and shade.
6. Never leave children or pets in parked cars even with the windows open. Temperatures can reach 130 degrees in a vehicle in only a few minutes.

The five-day forecast for St. Mary’s County:

Today: Mostly sunny and hot, with a high near 97. Heat index values as high as 108. Calm wind becoming south between 5 and 8 mph.

Tonight: Clear, with a low around 78. South wind between 5 and 8 mph becoming calm.

Wednesday: Sunny and hot, with a high near 99. Heat index values as high as 114. North wind between 5 and 7 mph.

Wednesday Night: Clear, with a low near 79. South wind around 5 mph becoming calm.

Thursday: Mostly sunny and hot, with a high around 97. Calm wind becoming west between 7 and 10 mph.

Thursday Night: A slight chance of showers and thunderstorms after 2am. Partly cloudy, with a low around 76. Chance of precipitation is 20%

Friday: A chance of showers and thunderstorms, mainly after 8am. Mostly cloudy, with a high around 88. Chance of precipitation is 40%.

Friday Night: Mostly cloudy, with a low around 74.

Saturday: Mostly cloudy, with a high near 86.

Saturday Night: Partly cloudy, with a low near 74.