On any given day the winds may vary, but - -
Prevailing winds are overwhelmingly from the west.
Especially in the summer.

Early morning is the best time to ride against the prevailing wind direction -
as winds tend to strengthen with the heat of the day.
But not always.

Here is a wind rose page from Iowa State University for The Dalles, Oregon.
It covers 45 years. Hood River doesn't have wind rose data, Cascade Locks very little.

IEM :: Site Wind Roses