It's thought the severe weather conditions are the worst to hit the country for three decades.
Hundreds of soldiers have been called in to flood-damaged areas - and three days of mourning have been declared.
Forecasters say a year's worth of rain fell in just eight hours in Valencia.
63-year-old Javier Berenguer owns a bakery there:
"I had to get out of a window as best I could, because the water was already coming up to my shoulders. I took refuge on the first floor with the neighbors, and I stayed there all night, keeping an eye out. It's taken everything. Everything."
