Extreme heat is impacting states across the country. See maps of high temperature forecasts and heat index levels.

An "extreme heat warning" has officially been issued for nine major U.S. cities on Monday, June 23. The National Weather Service is warning nine major U.S. cities of dangerously high temperatures beginning on Monday.

Harford County is opening 11 cooling centers for those looking for a reprieve from the extreme heat in Maryland this week.