The UK's travel lists are set to be updated later, with European countries considered mostly safe from being added to the red list.
However, changes could be on the way for other nations, according to data expert Tim White.
Mr White sees Morocco, St Lucia and Jamaica as the most likely holiday destinations to turn red, while there could also be changes for Croatia, Slovenia and Madeira.
There are currently 60 countries and territories sitting on the UK's red list, with the names being updated around every three weeks.
While he thinks most European destinations are safe from the red list - which means 10 days of hotel quarantine on return to the UK - Mr White said some could move from green to amber.
That would mean extra testing and home quarantine for those who are not double jabbed.
Mr White said: "The government retained the green watchlist which we assume means no country can go straight from green to amber, right? Well it happened before, so who knows?
"I was, I think, the only person who predicted Croatia would be moved to green a while back, and now many are writing that it's likely to move back to amber. I can agree with that.
"But again, let's compare with Germany which is on solid green. Croatia does around 75% more testing than Germany, yet its infection rate is less than 20% higher.
"Germany has done much better with administering vaccines, so that comes into play and maybe explains why it will stay green, while Croatia may go on the amber list."
Mr White said Bulgaria has the "full green traffic light rating" and yet COVID rates are 70% above Croatia and has lower vaccines and testing numbers.
"So it would be crazy for Croatia to receive a lower classification than Bulgaria," he said.
"Probably both should go from green to amber, but will the transport secretary move a nation from green to amber without the watchlist, and if he does so, what is the point of any watchlist?
"Slovenia too was only recently given the green light, but rates are soaring in the Balkans and are around 50% higher than Croatia, so it too is at real risk of being downgraded, but maybe only to the watchlist."
Other nations also face being moved, according to Mr White.
"Madeira, too, may face reclassifying, to match mainland Portugal's amber status," he added.
"Also many Caribbean destinations are fearful of changes in the upcoming review.
"Antigua and Barbuda, and Dominica, are most likely to have their green status removed, while Israel too seems almost certain to slip back to amber."