Nearly 400 firefighters and soldiers struggled against 82 wildfires in Cantabria, a sparsely populated region whose terrain is sliced up by deep mountain valleys, the regional government of Cantabria said.
At least 2,000 hectares (5,000 acres) of "extraordinary ecological value" has burned in the region over the past week, much of it located in two natural parks, it added in a statement.
"This threatens the present and future of Cantabria's landscape," the head of the regional government of Cantabria, Miguel Angel Revilla, said after visiting the site of one of the blazes.
He added that "99 percent" of the fires were deliberately set.
"There are arsonists, people with bad intentions who are taking advantage of weather conditions never seen before in Cantabria" to set fires, Revilla said.
Cantabria has since September received scant rainfall with average high temperatures of 23 degrees Celsius (73 degrees Fahrenheit), he said.
Strong winds, with gusts of up to 110 kilometres (70 miles) an hour were fanning the flames and preventing the use of water-dropping planes, Revilla said.
Wildfires near Basque town of Berango. Photo: Ander Gillenea / AFP
The national weather office predicts winds will remain strong, with temperatures way above average for this time of year in the coming days.
The army deployed 287 soldiers and 28 water tanker trucks to the worst affected area near the mountain village of Barcena Mayor, the defence ministry said in a Twitter message.
The government in the neighbouring region of Asturias in northwestern Spain said 38 wildfires were burning within its boundaries, including 31 which firefighters had under control.
Two wildfires were burning in the northeastern region of Navarra on the border with France.
A water-carrying plane tackles wildfires near Basque town of Berango. Photo: Ander Gillenea / AFP
The forest fires have so far claimed one life. A helicopter battling a fire in Asturias crashed on Wednesday, killing the pilot who was the aircraft's sole occupant.
Wildfires have destroyed more than 54,000 hectares (13,300 acres) of agricultural and forest land in Spain this year, exceeding the area burned over the previous two years combined, most of it in major summer fires, according to agriculture ministry figures.