The National Weather Service today issued a heat advisory for Washington, D.C., and parts of Virginia and Maryland.

The advisory, declared at 2 p.m., was extended by two hours to 8 p.m., according to the latest bulletin from the weather service.

On Thursday, a heat advisory will be in effect from noon to 8 p.m., the service said.

The weather service put today's peak temperatures in the middle 90s, but said high humidity would combine with the heat to produce heat index values around 100 degrees during the afternoon and early evening hours.

The service cautioned that the combination could cause "heat injuries" and urged people to drink plenty of fluids, stay out of the sun, check up on relatives and neighbors and avoid leaving children or pets in cars.

The heat advisory covers Washington's close-in Northern Virginia suburbs, as well as Baltimore.

Temperatures in the mid-90s and heat index values around 100 were also forecast for Thursday.

At Washington Reagan National Airport, today's high hit 93 degrees at 3 p.m.

The weather services predicts a slight cooling off during the weekend, with highs in the mid-80s both days and a chance of showers and thunderstorms on Saturday.