Police are advising motorists to avoid the A127, particularly at the Rayleigh Weir, which remains flooded after Saturday's heavy rain.
Officers are working with the local authority to get the water pumped away and reopen the road as soon as possible.
Over 200 incidents of flooding were reported to police on Saturday with areas worst affected including Southend, Canvey, Maldon, Burnham, Battlesbridge and Benfleet.
More top news
A drug and alcohol abuse charity has warned a new law making psycho-active substances illegal won't necessarily solve the problem.
This weekend's show is the first to take place there since new rules came into force after the Shoreham aircrash.
The family of two little girls who were left paralysed following a crash say they will never forgive the driver who caused the collision.