 This is WFMD News. The National Weather Service has put a heat advisory in effect until 8 o'clock tonight. Heat index values could be up to 109 degrees, and the hot temperatures and high humidity may cause heat illnesses to occur. The heat advisory covers Frederick, Carroll, and northwest Montgomery County, as well as western Loudoun and eastern Loudoun County in Virginia, and that also includes Frederick, Ballinger Creek, Westminster, Germantown, and Damascus.