Deaths were reported in the capital Riyadh, Baha in the south, Hail in the north and in the west of the country.
The Saudi Civil Defense Authority urged people to avoid valleys and plains that have been flooded by the heavy rainfall that began on Friday.
Saudi television showed footage of people clinging to trees and cars trapped by water.
The rain is said to be the heaviest experienced by the desert kingdom in more than 25 years.
On Sunday, Saudi Interior Minister Prince Mohammad Bin Nayef called on civil defense authorities to coordinate their efforts and provide assistance to people affected by rain and flooding.
Saudi authorities have been criticized in the past for lack of preparedness in coping with flooding. Flash floods in the Red Sea port of Jeddah killed 123 people in 2009 and 10 in 2011.
The inability of Jeddah's infrastructure to drain off flood waters and uncontrolled construction in and around the city were blamed for the high number of victims in 2009.
At the time King Abdullah promised action saying "we cannot overlook the errors and omissions that must be dealt with firmly".
However critics have said that despite the promises little has been done to alleviate the dangers posed by flash floods.