More than 1,400 residents of the southern town of Odemira were asked to leave yesterday, as around 800 firefighters fought the spread of the blaze.
So far, nine personnel from the fire teams have been injured while tackling the flames, which are quickly spreading south towards the Algarve.
On Monday, Portugal’s hottest temperature of the year was recorded in Santarém, north-east of Lisbon, where the heat reached 46.4C.
Weather forecasters predict much of the Iberian peninsula will be hit by temperatures of 40C or more this week.
The Odemira fire has destroyed around 16,600 acres of land, with the town’s mayor Helder Geurreiro describing the situation as ‘critical, difficult, and complex’.
Four hotels and a campsite in the area have been evacuated, leaving more than 100 tourists searching for somewhere new to stay.
Civil Protection secretary of state Patricia Gaspar told a news conference: ‘The weather conditions we are going to experience in the coming days means any small occurrence [fire] could become a big one.’
The Portuguese national weather agency IPMA has put around half of the country at the highest warning level for rural fires, including most of the central and north-east regions as well as the far south.
Another wildfire in the Castelo Branco area at the weekend was tackled by more than 1,100 firefighters with the help of 14 water-carrying aircraft.
Smoke from the blaze drifted 60 miles to the Fátima Sanctuary where Pope Francis was addressing pilgrims on Saturday.
Many places in southern Europe have been affected by wildfires in recent weeks as blistering heatwaves continue to linger.
Almost 2,500 acres of land were burned over the weekend in Spain, from the south-western city of Cadiz to the region of Catalonia in the north-east.
And last month, fires on the Greek island of Rhodes required the evacuation of more than 20,000 locals and holidaymakers – the biggest such effort ever undertaken in the country.
The ‘El Niño’ phenomenon has exacerbated the worsening effects of climate change this year, forcing temperatures up close to European records.
Impacts have been felt around the planet, with forest fires also spreading widely in North America.
On July 27, UN Secretary-General Antonio Guterres declared the era of global warming had come to an end and the ‘era of global boiling has arrived’.
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