Bournefest, a family-friendly music festival on Eastbourne seafront, had been due to open on Saturday.
However, a delay was first announced at 2pm, before organisers later confirmed the event would not go ahead as planned.
In an update issued shortly after 5pm, organisers said they had made the “incredibly difficult decision” to postpone the festival on health and safety grounds.
The announcement came just hours after festival organisers delayed the opening while they assessed conditions following wet weather.
The decision came less than 24 hours after a 41-year-old man from Eastbourne died at Big Church Festival at Wiston Park, near Steyning.
In a Facebook post, Bournefest said: “Due to unsafe weather conditions, we have unfortunately had to make the incredibly difficult decision to postpone today’s BourneFest event.
“We want everyone to know that we have done everything in our power to make this event happen.
“Our team has been working tirelessly behind the scenes, and this was not a decision we wanted or took lightly.
“This was not our decision but for health and safety we could not take the chance.”
Organisers had earlier said staff had worked “tirelessly” during the previous 48 hours to build the site and prepare for the festival.
The event features live music, tribute acts, food and drink stalls, family entertainment and camping over the bank holiday weekend.
In comments posted before the postponement was confirmed, organisers stressed they were doing everything possible to make the event happen.
One comment said: “This situation is completely out of our hands and not up to us. It’s up to health and safety. All artists are still en route and we will keep you updated.”
Bournefest organisers said they are now working to arrange a replacement date and expect to confirm it within the next three to four weeks.
The statement added: “We are working hard to confirm a new date within the next 21-28 days, and we will announce the new date as soon as it is confirmed.”
Ticket holders will be able to use their existing tickets for the rearranged event.
Organisers said: “Tickets will remain valid for the new date.
“If you are unable to attend and would like a refund, refund requests can be made within 28 days.
“All refunds will be handled directly by the point of purchase, including online ticket sellers and Skiddle.”
The Bournefest team thanked supporters for their patience and understanding, adding: “Thank you for your understanding, patience and continued support.”