Temperatures will reach near 90 degrees across much of New Jersey on Monday, and persistent high heat and humidity could produce severe thunderstorms again later in the day, according to the National Weather Service.

Although no alerts have yet been issued, the weather service says a “slight” risk of scattered severe thunderstorms is possible in areas below Interstate 78 between 3 p.m. and 9 p.m. Monday, with potential damaging wind gusts reaching 60 mph and large hail. Localized flash flooding is also possible.

Areas of South Jersey could hit the low 90s on Monday, while Jersey Shore temperatures will remain in the 80s. But, heat indices – a measure that combines air temperature and relative humidity – could hit some of their highest levels so far this year, officials said.

Heat indices could reach the mid-90s to nearly 100 degrees in parts of South Jersey and the Weather Service is warning those spending long periods outdoors to stay hydrated.

It’s a long holiday weekend for many, and the Jersey Shore will see a mix of sun and cloud today, according to forecasts. But, all are urged to keep an eye out for stormy weather this afternoon and evening.

Scattered thunderstorms are again expected for July 4th.

Our journalism needs your support. Please subscribe today to NJ.com.

Matt Gray can be reached at mgray@njadvancemedia.com.