The National Weather Service has issued a Heat Advisory for Montgomery, Howard, Baltimore, Prince George's, Anne Arundel, Charles, Washington, Frederick, Carroll, St. Mary's, Calvert, and Harford Counties as well as Baltimore City on Friday from 11 am to 9 pm. Heat index values around 105 degrees. Temperatures in the upper 90s to around 100 degrees. Risk of heat exhaustion or other heat releated illness for those without air conditioning or those spending time outdoors for an extended period.