Holidaymakers say they face losing work or cancelling holidays after new rules mean people returning from Spain must self-isolate for 14 days.
The Welsh Government has removed Spain from the list of countries exempt from quarantine, following a decision to do the same by the UK government.
In response, the UK's biggest tour operator, Tui, which flies from Cardiff Airport, has cancelled all mainland Spanish holidays until 9 August.
It follows a spike of cases in Spain.
The Foreign and Commonwealth Office (FCO) is advising against all but essential travel to mainland Spain. Quarantine measures apply to those returning from mainland Spain, the Canary Islands and the Balearic Islands, such as Majorca and Ibiza.
So how has it affected holidaymakers?
'I've had to cancel jobs'
Adrian Corbett, 55, of Caerphilly, is staying in a private villa just outside Valencia with his partner Claire Moriarty, 47, from Cardiff, and her two children.
He is a self-employed plumber while she works in mental health services as well as being a part-time hairdresser. They are due back to south Wales tomorrow.
"We didn't cancel the holiday because Ryanair wouldn't have given us a refund for a flight that was still operating," said Mr Corbett.
"However we would never have come out had we known there was an inkling the rules were going to change.
"I was gobsmacked when I saw the news because it's really going to cause us problems.
"I've had to cancel jobs booked for next week and Claire has two jobs that will be affected. She's already had four months without hair clients and now is facing two more weeks. Financially this is really going to hit us hard.
"The irony is that we've actually felt safer out here than in the UK. We're in a private villa, we've had less contact with people than back home and here, everyone wears masks everywhere."
Sheren Pugh, 32, from Crynant, Neath, and her friend only booked a holiday to Ibiza on Thursday and feels there should have been more warning that a rule change was on the cards.
"I'm gutted. I was really looking forward to going. I was super excited," she said.
"I live on my own so it's been tough in lockdown but I was going for four days of partying. We were planning on seeing Craig David on Tuesday but that's out of the window now.
"I'd booked the transfers, flights, hotel, there's just so much to sort out. We seem to have lost a lot of money.
"I work at a small dental practice so it won't be easy at all to get two weeks off again with staffing. I can't see me getting a holiday this year now."
'We're still going'
Rachael Gillespie, 48, of Llandough, Penarth, said she still intends to travel to Quesada, Murcia, on Monday morning, with her partner and two daughters, despite the warning.
"I'm not ignoring the potential risk but we're staying in a family villa, have a family car and both my partner and I are fortunate to be able to work from home when we return," she said.
"We'll also be staying a long way from Catalonia where the worst of the outbreak appears to be in Spain.
"I know there's a question over insurance and some people think I'm mad, but when you see the crowds in UK destinations like north Wales or the Lake District, where exactly is the safest place to holiday right now?"
Cancelled birthday holiday
Neil Payne, from Conwy, and 12 members of his family were due to go to Majorca, Spain, at the end of August to celebrate his 50th birthday.
This latest announcement has made up their minds following months of wrangling over whether or not to travel.
"My partner, Hannah, is a childminder and she can't afford to go and lose two more weeks' work when we get back and then there's the kids and school.
"My mum and dad are both over 70 and they have a wedding to go to just after they get back so my mum would be worrying about it.
"We have been anxious thinking 'do we, don't we go?'
"We are happier now we have made the decision to cancel the holiday but now we have to try and sort out the flights and the insurance company do anything they can to get out of paying."
What do the UK and Welsh governments say?
The foreign secretary has defended the "swift decision" to require travellers arriving in the UK from Spain to quarantine for 14 days.
Dominic Raab said he knows it will cause disruption for holidaymakers but the government "can't make apologies".
Labour's Jonathan Ashworth called the handling of the move "shambolic".
The new coronavirus travel rule was announced on Saturday following a spike in the number of new cases in Spain, with more than 900 reported on Friday.
The Welsh Government followed suit by removing Spain from the list of countries exempt from the 14-day quarantine rules and has issued details on how to self-isolate.
It said it was up to the police to enforce the quarantine.
Health Minister Vaughan Gething said: "I am amending our international travel regulations with effect from midnight [Saturday] due to the public health risk involved. This will reduce the risk of the transmission of the virus here in Wales.