Forecasters say Thursday temperatures could reach 100, with a heat index of 105 degrees.

Temperatures are expected to start cooling down on Friday and through the weekend. Saturday and Sunday highs should be in the 80s, according to the National Weather Service.

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The first day of summer is pouring on the heat. The National Weather Service has issued a heat advisory for Wednesday from noon to 8 p.m. for Northern Virginia, as well as the surrounding Washington, D.C. and Baltimore areas.

Temperatures are expected to rise to the mid-to-high 90s, but high humidity will make it feel as hot as 105 degrees, forecasters say.

Fairfax County recommends several ways to keep cool during the extreme heat, including drinking lots of fluids, staying in the shade or indoors in air conditioning, and exercising outside only during morning and evening hours.

Temperatures are expected to continue in the 90s through Thursday.

Summer officially arrives this evening at 7:09 p.m.