The National Weather Service has issued a heat advisory for most of the state, and the New Hampshire Department of Environmental Services is expecting unhealthy air quality for sensitive groups along the Seacoast on Thursday.

The heat advisory is in effect from 1 p.m. to 7 p.m. Thursday for Belknap, Cheshire, Hillsborough, Rockingham, Merrimack, Carroll, Grafton, Strafford and Sullivan counties.