Outsiders are being encouraged to stay away from Lewes on November 5 and celebrate Bonfire Night elsewhere.
Malcolm Richards, Sussex Police planning officer and a member of the Lewes Bonfire Safety Group, said: "We are concerned about the large number of people who may try to pack into the narrow streets of the town.
"We would urge people to attend their own local celebrations. Crowds can make this historic event very unpleasant and can raise potential risks."
Mr Richards said parents with young children, the elderly or those who dislike crowded environments should think twice about attending.
He said: "All those people who live outside Lewes and who were planning to come to the town should seriously reconsider."
South Central Trains will be providing extra services as a contingency measure to allow for a swift evacuation of Lewes should the need arise.
There will be no additional services provided to get people to the town before the celebrations.
A Bonfire Night information line has been set-up by Lewes District Council. Call 01273 484184.
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