Some 1,600 firefighters backed by 500 vehicles were battling 11 blazes that were burning out of control in the centre and north of the country, the civil protection agency said on its website.
Another roughly 800 firefighters were at the scene of 38 other blazes which had been tamed or were being dampened down, it added.
The fires come after more than 60 people were killed in June, and more than 200 injured, in a giant blaze at Pedrogao Grande in central Portugal that raged for five days.
Firefighters had brought the biggest blaze which broke out in a forest near the central town of Abrantes largely under control, Abrantes mayor Maria do Ceu Albuquerque told reporters at the scene.
"There are still two active fronts which are a cause for concern. But there is no wind and the conditions are reunited to have a calmer night and tomorrow we can put out this fire," she said.
Some 800 firefighters backed by 250 vehicles were battling the blaze, which broke out on Wednesday as the return of scorching temperatures put an end to a brief respite from a spate of blazes.
The fire reached an industrial park on the outskirts of Abrantes and forced the evacuation of four nearby villages as a precaution.
'Burned all day'
Roughly 50 residents of the villages will spend the night at a military building, Albuquerque said.
"It has burned all day. It started up high and the flames went all around," Matilde Simao, a resident of evacuated village Pucarica, told AFP.
Firefighters said low air humidity levels and strong winds, which frequently changed direction, had complicated their initial efforts against the blaze.
"There are people setting fires, bad people. It is the only explanation that I can see, there is no other," said Maria Conceicao, another resident of Pucarica.
Local residents used garden hoses and plastic buckets full of water to help firefighters put out the flames.
Weather conditions will be "especially favourable for wildfires" until Sunday, with strong winds and temperatures of up to 39 degrees Celsius (102 Fahrenheit) forecast, civil protection agency spokeswoman Patricia Gaspar told a news conference.
Morocco sent a water-dropping plane and neighbouring Spain sent two to help firefighters battle the flames, she added.
Another fire near the northern village of Mealhada forced the closure of a 30-kilometre (18-mile) stretch of the A1 highway linking Lisbon and Porto, Portugal's two largest cities, for several hours.
The railways linking Lisbon to the southern province of the Algarve, a popular European beach destination, was also closed for several hours because of a blaze near the city of Grandola.
Police said they had arrested a 61-year-old man who is suspected of having started a fire near the central village of Lordelo.
The president of the Portuguese Firefighters' League, Jaime Marta Soares, told private television SIC he believed more than 80 percent of wildfires in Portugal had a "criminal origin".
After an uncommonly dry winter and spring, almost 79 percent of the Portuguese mainland was enduring extreme or severe drought at the end of July, according to the national weather office.
Dry conditions were also fuelling a wildfire on France's Mediterranean coast.
About 200 firefighters backed by six water-dropping aircraft battled a blaze in Port-de-Bouc west of Marseille which was threatening built up areas, local firefighters said.
