A 9-year-old girl was among the dead, and other victims were found drowned in their vehicles, thinkSpain reported.
The worst flooding Friday was in the regions of Andalucia and Murcia.
A woman in the town of Guadalhorce, in Andalucia's Málaga province, was close to a river when it overflowed its banks. She and 12 other people, including her husband, were washed down the street.
In Murcia, a 9-year-old girl drowned when the vehicle in which she was traveling was washed off the road by flash flooding. Two other people in the car were able to escape.
A bridge on a highway between Lorca and Puerto Lumbreras collapsed Friday afternoon, but no one was hurt. Another bridge collapsed in Almeria, one of the areas most affected.
Just plowed farmland was inundated, although it had not yet been seeded.
Officials said at least 600 people had to be evacuated from their homes in the Andalucia region, the BBC reported.
About 9.6 inches of rain fell Friday morning alone, Spain's weather agency said. The country has suffered through months of drought and high temperatures.
The rain and violent thunderstorms were expected to continue through the weekend.