Cornwall has urged people to stay away unless they have pre-booked their trip amid a sharp rise in COVID-19 cases in the county.
The chief executive of Visit Cornwall, Malcolm Bell, said visitors who do come should test themselves extensively and aim to "treble their efforts as much as possible" with the hands, face, space guidance while trying to remain outdoors.
"We are asking people not to come unless they have booked ahead and request they take a lateral flow test before, during and after (their) stay so that (people) can be safe and help us to manage the current spike," Mr Bell said.
Both Devon and Cornwall had 500 cases or more per 100,000 people in the seven days to 18 August, according to figures calculated by the PA news agency.
The figure was 300 or less per 100,000 people a week before.
It comes after health officials said they were investigating 4,700 cases that are suspected to be linked to the Boardmasters festival, which took place nearly two weeks ago in Newquay.
Mr Bell said: "There is concern and most local residents will be happier in a week or so, when the peak season is over and an older demographic visits as there are too many occurrences of overcrowding in honey pots.
"We are asking visitors to look at visiting other parts of Cornwall.
"We have over 300 beaches and lovely parts that can cope with visitors."
He said the vaccination programme in the county was in "full flow".
The mayor of Newquay, Louis Gardner, who also owns a deli in the town, said he has been speaking to other businesses who believe the rise in cases is due to a number of different issues.
"We're seeing a spike in Cornwall because we've got the highest number of visitors we've ever had," said Mr Gardner, who is also the Conservative councillor for Newquay Central and Pentire.
"Our accommodation is at 100% capacity, our hospitality venues are full, there's no social distance in place, but I think those factors all added in all together are having an effect.
"It's a perfect storm."