The worst-affected region of Cantabria, where nearly 700 firefighters, soldiers, police and volunteers struggled against wind-fuelled fires that came dangerously close to remote villages, said the fires had been put out although zones of "dying embers that are under control" still remained.
In a statement, the local government said rain had finally fallen on a region hit by unseasonably warm weather.
Emergency services in the nearby regions of Asturias and Navarra, also hit hard by wildfires, said blazes there had been extinguished or were under control.
The forest fires have devastated swathes of northern Spain and claimed one life - that of a helicopter pilot who crashed last week as he battled a fire in Asturias.
In Cantabria, at least 2,000 hectares (5,000 acres) of "extraordinary ecological value" burned over the past week, much of it located in two natural parks.
The head of the regional government, Miguel Angel Revilla, said 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, he added.
In its statement, the government said emergency services remained on high alert in the region, with winds and high temperatures expected to make a comeback.
Soldiers and emergency workers were to continue patrolling the area "to act as deterrents."
Altogether, wildfires have destroyed more than 54,000 hectares of agricultural and forest land in Spain this year, exceeding the area gutted by fire over the previous two years combined, according to agriculture ministry figures.