A considerable part of Washington and Oregon experienced on April 21–24, 1931, an extraordinary dust storm borne on strong northeast winds that were common to both States, although of greater force in some parts than in others.
A week previous saw the end of a rather protracted wet spell in both States which was succeeded by clear skies very low relative humidity under which the top layers of the soil had dried out very thoroughly so that the strong northeast winds that occurred on the 21st whipped up great quantities of dust from the wheat country and the semiarid parts of the interior and carried westward and southward as a dust cloud of great magnitude that subsequently blew itself out over the Pacific Ocean. The strength of the wind was such as to overcome and blow down frail structures and even great trees. So high winds were quite exceptional for the time and place. Forest and brush fires broke out suddenly over much of the territory invaded by the dust storm; the very low relative humidity and poor visibility made fire suppression very difficult.
The winds subsided during the night of the 22d and 23d and during the daylight hours of the 23d but a smoke pall continued for several days in the territory affected.