The national weather authority, IPMA, has put the entire Portuguese mainland on alert until Monday.
Around 200,000 customers are still without power several days after Storm Kristin swept across the country, resulting in five deaths.
Portugal's civil protection agency warns that the new rainy weather could cause flooding in urban areas and trigger landslides and rockfalls.
Prime Minister Luis Montenegro declared a state of disaster on Thursday, a level below a state of emergency, for the hardest-hit areas.
