Floods can occur in any month, but most commonly occur between November and February during periods of heavy rain or rapid snow melt. During a flood, agencies respond in four phases depending on the severity of expected flooding, with Phase 4 being the most severe.
During phases 2, 3, 4, flood updates and warnings are reported to police, fire departments, schools, other agencies, and news media.
See left sidebar for phase and river levels at gauge sites in Snohomish County.
Actual flooding is rare
County staff is put on alert
Preparations are made to open the county's Emergency Operations Center
Minor flooding and some road closures may occur
The county Emergency Operation Center opens
Staff begins monitoring river gauges and flood conditions around the clock
Flood information phone lines are updated hourly with current river gauge / river level information
Moderate to severe flooding, with numerous road closures and some levee overtopping can be expected
Investigation crews are sent to monitor flood control facilities such as levees
All agencies respond in anticipation of major flooding and widespread damage