HARRISONBURG, VA (Rocktown Now) — The National Weather Service has issued a Heat Advisory beginning at 11am today until 8pm tonight.

Heat index values up to 103 degrees are expected throughout the valley in Rockingham, Page, Shenandoah, Clarke, Frederick, and Warren counties.

Hot temperatures mixed with high humidity could cause heat illnesses.

What’s a heat index? Your guide to summer heat warnings and how to stay safe