The mudflows began around 6 p.m. on August 16, 2004 after a heavy afternoon thunderstorm dropped rain and hail in the area. Sixty people were trapped by the slides, 25 fire crew members and 40 members of the general public. WSDOT crews were able to clear the road by midnight and those stranded were able to leave. No one was hurt and no vehicles were damaged.
Four separate slides blocked the road at mileposts 149, 150, 153 and 156, just west of Rainy Pass. At milepost 149, there was a 300-foot wide slide approximately eight feet deep. At milepost 153, the 300-foot slide was approximately 10 inches deep.
WSDOT crews from Everett and Twisp attacked the slides from opposite sides of the pass. They removed all kinds of debris from the roadway, including wood, gravel, and boulders the size of car engine blocks.
The highway was reopened August 19, just three days after the mudslides happened.