The storm caused minimal wind damage, but it struck a part of the country rarely affected by tropical cyclones, which made it more vulnerable to the disaster.
Washi was one of the most deadly storms to hit the country since Fengshen killed 938 in the central Philippines in 2008.
The bulk of the fatalities associated with Washi occurred around the cities of Cagayan de Oro and Iligan, where more than 275,000 people were made homeless.
The storm produced more than 7 inches of rainfall across the area.
"This is the first time this has happened in our city," Vicente Emano, mayor of Cagayan de Oro, said in a radio interview.
He added that there was not adequate warning of the storm’s potential impact before it moved ashore from the Philippine Sea.
His city delayed a mass burial of many of the victims to allow police to tag more than 600 recovered bodies for identification.
Washi had formed a week earlier in Micronesia, then dissipated off the coast of Vietnam after soaking Mindanao.
Tropical Storm Washi Track
Satellite Loop Data: CIMSS