Mount Rainier

Mount Rainier

Did you know Mount Rainier is an active volcano?  While we can't say how many times Rainier has erupted over the course of its existence, we do expect it to erupt again someday.  The only questions is matter of when, and to what degree.

A Mount Rainier eruption will place the Puyallup valley at risk of catastrophe from a lahar, which is a volcanic mudflow that can reach 100 feet in height and travel 45 to 50 miles per hour. According to the United States Geological Survey (USGS), "Lahars look and behave like flowing concrete, and they destroy or bury most man-made structures in their paths." 

Should Mount Rainier erupt, everyone in the valley will need to avoid the oncoming lahar by evacuating to higher ground. It's for this reason that the lahar warning siren system is tested on the first Monday of each month, and it's also why we provide a map showing recommended Volcano Evacuation Routes.

Learn more about Mount Rainier and lahars, courtesy of the USGS.

Bridge destroyed by lahar North Fork Toutle River

Bridge destroyed by lahar in North Fork Toutle River during eruption of Mount St. Helens, May 18, 1980.  (Credit: Waitt, Richard. Public domain.)

Evacuation Routes & Hazard Maps

Lahar Warning System

Upgrade & Expansion Project

Pierce County Department of Emergency Management (PCDEM) expanded the number and reach of the outdoor warning sirens in 2020. PCDEM has 42 sirens in the Puyallup River Valley and the Nisqually River Valley. The recently upgraded sirens will have more capabilities to notify people of emergencies. They include voice warnings in English and Spanish, flashing lights to reach vulnerable populations, and verbal instructions based on the emergency.

Testing happens the first Monday of each month.  The new test siren will sound similar to a Westminster chime on a clock. You can hear the tone and verbal instructions for the test by clicking here.

To learn more about the updates, visit Pierce County Department of Emergency Management.

Upcoming Webinars

Volcano Webinar

Join this FREE webinar to learn about the five active volcanoes in the Washington Cascades, their hazards, and how you can be better prepared for an eruption!

Thursday, May 13, 2021

1:00 p.m. to 2:30 p.m. (PST)


Captions available.  Questions?  Email  More info at

Unable to attend the live webinar?  Fear not!  A link for the presentation will be posted on the Washington State Emergency Management Preparedness webpage.