Eight places in the centre, south and east of Portugal have broken their local temperature records as Europe swelters.
On Thursday, temperatures reached 45.2C (113.4F) near Abrantes, a town in the centre of the country.
They are set to build across Portugal on Friday and Saturday, with medical staff and firefighters on standby until the end of the weekend.
In Spain, heat warnings were also issued for 41 of the country's 50 provinces as temperatures were expected to reach up to 44C (111.2F).
Temperatures in south-west France could also rise to the high 30s.
The mercury is being driven higher by a hot air mass moving north from Africa, bringing dust from the Sahara Desert.
The next few days could see the hottest temperatures recorded in continental Europe.
Luke Miall, a Met Office meteorologist, said the record is 48C (118F) in Athens, Greece, in 1977.
Tourists were urged to avoid the sun during the hottest part of the day and remember that children are particularly susceptible.
A spokesman for the travel trade association Abta said: "We would advise any tourists setting off to the Iberian peninsula, or anywhere else this weekend where they may experience high temperatures, to take a lead from the locals and avoid spending time in the sun during the hottest part of the day, drink lots of water and apply plenty of sun cream.
"If you go to the beach, go early and when it feels like it's getting too hot leave, just as the locals do, and go and have a nice lunch in the shade. The reason they do this is because they know how powerful the sun can get in the hottest part of the day and they do everything they can to avoid it."