The week’s highest temperatures of around 38C (100F) are expected on Tuesday and together with windy conditions could reignite fires already quelled.
Civil protection officials say although 70% of the fire is under control, what remains is a source “of great concern”.
At least 64 people have died in the fires since Saturday.
The latest of the victims was identified as a 40-year-old firefighter who died in hospital.
Many died inside their cars or a short distance away from them as they tried to flee. More than 130 other people have been injured.
The government has declared a state of emergency in the forested region around Pedrógão Grande, north-east of the capital, Lisbon.
Civil Protection commander Elisio Oliveira said there was great concern for the fires still burning. He described the operation as “complex” and said many residents were being forced to evacuate.
More than 1,000 firefighters are tackling the blaze which continues to rage on several fronts.
One volunteer rescuer quoted by Reuters news agency said teams were not optimistic about bringing the blaze fully under control anytime soon.
“Low humidity, windy conditions and high temperatures will easily re-ignite the fire, and it will spread very fast,” he said.
When asked about the plan for Tuesday, he added: “It all depends on the weather.”
Police believe the fires were started by lightning on Saturday during an intense heatwave and rainless thunderstorms.
One of the worst-hit areas was around the village of Nodeirinho. Thirty bodies were found inside cars and another 17 next to vehicles on the N-236 road.
Portuguese media have dubbed the N-236 the “road of death”.
A few miles north, 11 people died in the village of Pobrais, many as they tried to escape the flames. A survivor spoke of the roads being blocked and of no-one coming to their aid.
Betty Jesus, a 50-year-old Venezuelan who has lived in the area for decades, said: “I have witnessed a lot of fires, but never like this. The way it spread, the speed.”
Virgilio Godinho, who lives in the village of Figueiro, said the fire quickly overwhelmed the community.
“The fire didn’t spread by the ground, it spread through the air at the height of the trees. In five minutes all were on fire in an area of around 10km,” he said.
Portugal is observing three days of mourning for the victims.