 Martinsburg to Hagerstown. This is brought to you by Frederick Air and Bryant. Whatever it takes to keep you comfortable, Frederick Air, it's a good call. The 930 WFMD sky scan forecast. Frederick and surrounding counties is a heat advisory, 11 a.m. to late p.m. This morning, clear skies. Set into partly cloudy and oppressive today with a couple of afternoon and evening thunderstorms. High 102, heat index 110. Partly cloudy otherwise tonight, low 76.