(Updated at 4:05 p.m.) Today’s heat advisory has been extended through 10:00 p.m. on Thursday. From the National Weather Service:

… HEAT ADVISORY REMAINS IN EFFECT UNTIL 10 PM EDT THURSDAY…

* HEAT INDEX VALUES… 100 TO 105 DEGREES TODAY AND AROUND 105 DEGREES THURSDAY. OVERNIGHT HEAT INDEX REMAINING ABOVE 80 DEGREES IN THE SUBURBS AND NEAR 90 DEGREES IN THE URBAN CENTERS.

* TEMPERATURES… HIGH TEMPERATURES TODAY AND THURSDAY IN THE UPPER 90S TO AROUND 100. LOW TEMPERATURES TONIGHT IN THE MID 70S AND LOWER 80S.

* IMPACT… THOSE OUTDOORS FOR AN EXTENDED PERIOD OF TIME AS WELL AS THOSE PARTICULARLY SENSITIVE TO THE HEAT WILL BE AT RISK FOR HEAT EXHAUSTION AND OTHER HEAT-RELATED ILLNESS.

Arlington County has a list of “hot tips for keeping cool” on its website.

WMATA announced this morning that it is making an exception to its “no drinking” policy to allow customers to drink water on the Metro system.