Unlike other parts of the country, Seattle doesn’t have any regular catastrophic events to deal with on a yearly basis. We don’t have tornadoes. We don’t have hurricanes. We get a lot of rain and can sometimes get high winds (30-60 mph) during storms, but these don't usually result in disaster-level damages (although, fallen trees are no joke if you live under any tall fir trees).
But make no mistake—Seattle is not immune to major disasters. Quite the contrary, this region has the potential for major and massive natural disasters to strike, so major in fact that the entire region could even be destroyed if the worst-case scenario were to happen (think huge Cascadia Subduction Zone earthquake followed by an equally destructive 9.0 earthquake). From earthquakes to tsunamis, no matter how remote the chances are, it’s best to understand what could happen and how to be prepared.
Earthquakes are one of the most possible and present dangers facing Seattle at any given moment as Seattle and the wider Northwest region is marked by several fault lines. Right within the Seattle city limits is the Seattle Fault, which runs east-west across the Puget Sound and through Seattle, very roughly in line with I-90. Just to the south, the Tacoma fault (a series of connected fault lines) is also east-west and runs approximately from Allyn, then branches out over Gig Harbor, Ruston and the eastern shore of Tacoma, and Federal Way.
Just off the Washington coast is the Cascadia subduction zone, where the Juan de Fuca plate meets (and pushes underneath) the North American plate. The Cascadia subduction zone became a hotter topic after an article in The New Yorker in 2015 delved into the possibility of a megathrust 9.0 quake from this seismic zone.
These faults as well as other local fault lines, of which there are many, all contribute to the earthquake potential in the Seattle area.
With five active volcanoes in Washington—Mt. Baker, Mt. Rainier, Mt. St. Helens, Mt. Adams and Glacier Peak—the risk of a large-scale volcanic eruption is low, yet ever-present. Seattle is most likely to suffer damage from ash falling or lahars (massive, quick-moving mudflows) up the Duwamish River from a Mt. Rainier eruption. Tacoma and communities and towns at the base of Mt. Rainier are more at risk of destructive lahars, ash, and other dangers—some Pierce County cities are actually built situated on top of mudflows of the past. Pierce County cities such as Puyallup and Orting have Volcano Evacuation route signs and it is wise to be aware of your evacuation route.
Many Seattle-area residents may not think tsunamis could be a problem as Seattle is not on the coast. However, studies by the National Oceanic and Atmospheric Administration (NOAA) have shown that it is possible that a tsunami could result from an earthquake on the Seattle Fault, which runs underneath the Puget Sound. Such a tsunami could be as high as about six feet, which could cause major issues along waterfront areas in Seattle and even as far as Tacoma! With a large enough quake on the Cascadia Subduction Zone off the Pacific Coast, a tsunami could potentially reach the Seattle area as well.
The entire Puget Sound region has no shortage of water. When we get record rainfall or freak happenings such as king tides, floods are a natural-yet-disastrous occurrence. Depending on where you live, flooding may or may not be a problem that could impact you and your home. If you are buying a home, it is worth checking FEMA maps, FloodSmart.gov, and county records to know potential flood risk before you buy. If you find out your home is in a flood zone after you already own a home, knowing what to do in case of a flood is good to read up on in advance!
The Puget Sound area is not known for extreme weather, but residents of the region regularly face two highly problematic types of storms—windstorms and ice storms. While Seattle does not usually get hurricane-force winds, windstorms can bring strong gusts of up to 80 mph that often knock down power lines and leave branches and fallen trees in their wakes. At best, wind storms are a mess to clean up. At worst, a tree may fall on your property or knock out your power. In 2006, a wind storm took out power to 175,000 City Light customers!
Winter ice and snow storms bring an entirely separate set of problems along with them. Snow in the Puget Sound usually falls and melts soon after, but if it falls and immediately freezes or melts by day and freezes by night, many of the hilly streets in Seattle and Tacoma turn into hazard zones! Even a small amount of snow may slow or cripple activity in the area.
How to Prepare
While the Seattle and Northwest overall have some pretty scary natural disasters that could happen, the best course of action is to be sure you're prepared. For most disasters, the answer is knowing in advance what your escape routes are, knowing how you'd communicate with family or friends if phone networks go down, and having some emergency supplies on hand. Not sure how to prepare? The Red Cross has great information, including lists of emergency supplies, to help anyone be ready.