Tourists gave Brighton and Hove a multimillion pound boost by flocking to enjoy record October weather in the city.
Pubs and restaurants had to order emergency supplies as hundreds of thousands of people arrived for the unseasonable sun.
As new temperature records were set in the city, businesses saw their average weekend takings for this time of year double.
Adam Bates, the head of VisitBrighton, said he expected up to £5 million to have been spent in the city this weekend alone.
That is more than double the October weekend average.
Beaches in the city were packed as about 200,000 extra people crammed into Brighton and Hove.
Mr Bates said: “It has been a great way to extend the season which is clearly what we want.
“There have been events going on all weekend. It has been terrific.
“It will make a real big difference for local businesses, not just hotels and restaurants but all shops and attractions.”
The city's tourism website saw a 30% spike in visitor hits at the end of last week as people planned to enjoy the Indian summer by the sea.
The site was visited once every 15 seconds on Thursday and Friday and calls to Brighton Visitor Information Centre increased by more than 50%.
Brighton and Hove City Council said its seafront team was “experiencing one of its busiest autumns ever”.
Geoffrey Bowden, the council's cabinet member for culture, recreation and tourism, said: “This is a welcome fillip at the end of the season as tourism supports over 13,500 jobs in the city.
“Brighton and Hove always looks brilliant in the sunshine and it's no surprise that visitors headed our way to make the most of it.”
Many visitors sweltered in their cars as traffic into the city was bumper to bumper for miles on both Saturday and Sunday.
The Brighton Breeze Volkswagen camper van run on Saturday and the London to Brighton Land Rover Run added to the weight of traffic.
The Met Office said temperatures around Brighton peaked at 23C yesterday - the highest temperature ever recorded in the area in October.
However the weather did leave hospitals struggling to cope with the numbers of people suffering heat-related problems.
A spokesman for Royal Sussex County Hospital in Brighton said: “We have been a lot busier than we would normally expect for this time of year.
“Staff in the accident and emergency department have been working flat out.”