The mercury hit 24.7 degrees celsius, not far shy of the highest figure for the month on record for the town of 26.4 degrees in 1870.
Seafront ice-cream retailer Convex Leisure reported selling 3,500 cones and lollies to the sun-worshipping crowds.
Paul Metcalfe, lifeboat operations manager for RNLI Eastbourne Lifeboats, said, "It was a very busy weekend, the hot weather encourages the boating fraternity.
"A lot of boats were using Sovereign Harbour and a lot returning in the early part of the evening on Sunday.
"There were quite light winds so a lot of sailors were out and several power boats."
Despite the high traffic on the seas the lifeboats were only called out five times, to incidents including stranded boats which had lost power and a young girl who got into trouble swimming.
The swimmers were attracted by an unusually high sea temperature of 14.2 degrees.
Delso da Silva, of Treasure Island adventure park, in Royal Parade, said businesses on and around the seafront had brightened with the influx of people.
He said, "It's better than rain, it does help. It would be nice to have the sunshine through the rest of the season as we haven't had it for the last couple of years but, hey, at least it's not snow."
He added, "It was really good to see everybody out and about because it was so quiet during the Easter holidays when the kids were off.
"During the school holidays the weather was not good and the feeling I got was that there was not a lot of money about and people were nervous about going out and spending.
"I have been talking to quite a few people with businesses on the seafront and it has been very difficult for them. It has been very quiet but the weekend has definitely helped and shown businesses there is going to be light at the end of the tunnel."
Publicity for the town was also increased by the presence of BBC Breakfast, filming a feature on the Kidzsafe wristband scheme, which provides free waterproof wristbands for children with a space for parents' mobile phone numbers so if lost they can be reunited with their family.
Steve Wallis, Eastbourne Borough Council tourism spokesman, said, "With our record sunshine statistics and official status as sunniest place in the UK, the seafront was packed with people making the most of the good weather."