Festival-goers at Chicago's Lollapalooza were evacuated amid warnings of severe thunderstorms Sunday. Above, Metallica performs during Lollapalooza 2015 at Grant Park on Aug. 1, 2015. Tasos Katopodis/Getty Images

This story has been updated.

UPDATE, 5:16 p.m. EDT: Organizers say the Lollapalooza music festival will reopen, the Associated Press reported, following a thunderstorm and hail in the Chicago area.

A release from festival officials said gates would reopen at 3:30 p.m. local time (4:30 p.m. EDT) and the music would resume at 4 p.m. local time.

Original story below.

Attendees at the Chicago music festival Lollapalooza are being evacuated as thunderstorms approach Grant Park, where the concert is being held, on the final day of the three-day event. The National Weather Service has issued a warning and attendees were being ushered to emergency evacuation shelters, the organizers of Lollapalooza said in a statement.

The Chicago Weather Center issued a severe thunderstorm warning for Cook County, which includes Chicago, at 2 p.m. local time (3 p.m. EDT). “Some hail and strong winds are expected in portions of the city,” it warned. The hail could be the size of golf balls, while gusts of wind could reach 60 miles per hour.

The festival had been suspended “for a short period,” organizers said. “Lollapalooza officials are continuing to coordinate with the Chicago Office of Emergency Management and Communications to monitor weather conditions and determine when the park is safe for festival-goers to return,” it added.

“We regret having to suspend any show, but safety always comes first,” Sandee Fenton, the director of publicity for C3 Presents, which promotes Lollapalooza, said.

Lollapalooza is an annual three-day music festival in Chicago. This year it is being held from July 31 to Aug. 2. Headlining the show were artists including Paul McCartney, A$AP Rocky and Sam Smith and the bands Metallica, Of Monsters and Men and First Aid Kit.

The storms could continue through Sunday night, WLS-TV Chicago reported, although the National Weather Service’s warning extended through 3:15 p.m. local time.

An estimated 300,000 people were expected to attend Lollapalooza throughout the weekend, the Chicago Tribune reported.