Horsham workers have been advised to evacuate their office amid rising flood levels in the town.
The River Arun has burst its banks in multiple places including close to several houses and the Memorial Gardens are submerged in flooding.
Workers at Afon House in Worthing Road were advised to leave the building.
Several travel warnings have been issued with police urging motorists to stay at home.
There is also severe rail disruption and the M23 has been closed in both directions between junction 10 and 11.