Here's what we know so far.
Why might Portugal move to the Amber List?
Portugal was one of the very few destinations to be included in the green category last month, with Iceland the only other country on the list that is popular with visiting Scots.
But scientists from the Joint Biosecurity Centre (JBC) are concerned about rising infection rates and the the possibility of new variants being imported.
Portugal currently has around 37 Covid infections per 100,000 people, its worst numbers since March and higher than the UK’s figure of 34.5.
Boris Johnson has indicated he will follow the advice of the JCB, saying: “You've got to wait and see what the JBC says and what the recommendations are about travel.
"We're going to try to allow people to travel, as I know that many people want to, but we've got to be cautious and we've got to continue to put countries on the red list, on the amber list, when that is necessary.
"I want you to know we will have no hesitation in moving countries from the green list to the amber list to the red list, if we have to do so.”
When will an announcement by the UK Government be made?
Ministers are expected to update its travel advice later on Thursday after a meeting of the JBC.
It’s thought that a number of countries, including Malta, may be moved from the Amber List to the Green List.
What are the rules for Amber list countries?
Those arriving from an Amber List country must self-isolate at home for a 10 day period on return to the UK.
They must also complete a passenger locator form, take a coronavirus test before travelling, and book (and pay £170 for) a coronavirus travel test on the second day and eighth day of their isolation.
You must book these testing kits using the online CTM Booking Portal – the free lateral flow tests or those offered by private comanies are not acceptable.
Can I still go to Portugal if it moves to the Amber List?
There is no law that says that you cannot go on holiday to an Amber List country, as long as you follow the appropriate rules.
However, the Scottish Government advice states: “You should think carefully before booking travel to a country or area on the amber list for holidays or for any other leisure purpose. Travelling abroad carries a risk of bringing new cases and variants of COVID-19 into Scotland.”
And Prime Minister Boris Johnson has advised that people should not holiday in countries on the list, but refused to legislate against it.
Meanwhile, Nicola Sturgeon said: “We still intend to be highly cautious on international travel, given the risk of new variants, but we consider that the situation now allows us to begin a careful move away from blanket restrictions on non-essential travel. Everyone should think seriously about whether they really need to travel abroad this summer. I know for many people international travel is about family connections. But when it comes to holidays abroad, my advice continues to be to err on the side of caution and to staycation this summer.”