Turns out that fireworks themselves aren’t banned in southwest Snohomish County, just their use. We asked Snohomish County for an explanation and received this from Mike McCrary, Snohomish County Fire Marshall and Director of the Department of Planning and Development Services via email.
Fireworks discharge is not allowed for many areas in unincorporated Southwest Snohomish County where they have been allowed in years past, but county code allows for the sale of fireworks between noon on June 28 and noon on July 6 of each year. Banning the sale of fireworks in any part of the county would require a change in county code, whether or not their discharge is allowed.
This page has up to date information about the sale and discharge of fireworks: https://snohomishcountywa.gov/1164/Fireworks.
In the City of Everett not only is discharge banned but all sales and possession of fireworks have been illegal since 2002.
June 29, 2021
Everett Fire