The Foreign, Commonwealth and Development Office has warned UK travellers they may face delays at airports because of planned strike action by Portuguese immigration officers.
The walkouts are set to take place from May 31 to June 28.
The FCO said: “Days and times of strikes vary according to airport location.
“If you are travelling during this period, check with your airline whether you will be affected and allow more time to clear border control when entering and exiting Portugal.”
Portugal is the only mainstream summer holiday destination that is available to UK travellers thanks to its green list status.