Thai restaurant group Giggling Squid's Hove site has been forced to close after being deluged by hailstones "the size of golf balls", which tore through the roof.
All bookings for the next six weeks have been cancelled following the storm, which caused damage to all for four floors of the venue.
The repair bill is expected to be up to £150,000, owner Andy Laurillard told Brighton and Hove News.
"We have lost the ceilings and floors all the way through the restaurant, from the second floor to the basement. The electrics are out, the decor is knackered."
Regulars to the Hove site have been offered a discount at the nearby Giggling Squid in Brighton, while Laurillard promised a new and improved restaurant when it reopens.
He said: "We will be back. We are going to make it look amazing."