Skip to main content

Climate change impacts in King County

Climate change impacts in King County

Seawall at high tide

King County is already experiencing the impacts of climate change

Our climate is changing. Since 1900, average annual air temperature in the Puget Sound region has increased by 1.3 degrees F. Heavy rain events are getting heavier, we are experiencing a long-term decline in snow and ice in the Cascades and Olympic mountains, sea level is rising, summers are warmer, and ocean chemistry is changing in ways that are harmful to marine species. Additionally, climate change will harm people and communities differently across King County based on age, gender, health, where they live, and what they do for work. And rising greenhouse gas emissions will only accelerate these impacts and other changes in the coming decades, affecting the environment, communities and public health, and the economy and infrastructure.

Explore the infographic to learn more about how climate change is affecting our region.

Confronting climate change: how does a changing climate affect our region?

October 2017

Changes are already affecting our environment, economy and human health. The choices we make today about reducing greenhouse gases will affect the severity of future impacts.

Increased heat

Average annual air temperature in the Puget Sound region is increasing (+1.3F, 1895-2014), and is projected to be 5.5F warmer in the 2050s.

Public health impacts due to heat
  • More illnesses
  • Mor hospitalizations and deaths

Increased wildfire threat

Four-fold increase in annual area burned projected for Washington's forests by the 2040's.

Less snow

Average Cascade snowpack down 25% from 1950s to 2006, projected decrease of 55% in the 2080s.

Heavy rain events are increasing

By the 2080s, our heaviest rain events are expected to be 22% heavier.

Extreme river conditions

  • Summer - lower flows, warmer water
  • Winter - higher flows, flooding

Rising sea level - Seattle sea level rise

  • 1899-2016 - 9 inches increase 
  • by 2100 - 24 inches increase

More coastal flooding

Increased costs to shellfish growers due to ocean acidification.

Climate change impacts in King County part 1

Recent years offer a preview of future conditions if no action is taken.


January 2015: Warm storms bring torrential rain and flooding

Record low snowpack

Spring 2015: Record low snowpack in the Central Cascades. Four percent of average snowpack meant less water for people, agriculture and fish.

Record temperatures

2015: Hottest year on record for Washington State.

Summer 2017: Hottest and driest summer on record for Seattle.

Landslide risks

Winter 2017: Wettest winter on record creates flooding and landslide hazards throughout the Puget Sound region.

Poor air quality

Summer 2017: Smoke from northwest forest fires create unprecedented summer air quality problems in the Puget Sound Region. 

If we don't act now, the costs and consequences will grow


  • Increasing stress for salmon
  • Impacts on forests from insects, disease and fire
  • Changes in habitat important to local species
  • More harmful algal blooms in lakes and Puget Sound


  • Greater risks to homes, businesses, and infrastructure from increased coastal and river flooding.
  • Marine-based economies suffer as fish and shellfish diminish.
  • Increased summer drought stress.


  • Health impacts from heat exposure
  • Changes in illnesses carried by ticks and mosquitoes
  • Increased risks for people with asthma and heart illness due to more summer air pollution.
  • Greater risk of injury and property damage from more extreme weather.

Learn more about what King County is doing to confront climate change at For detailed source information, visit the sources page.

Climate change impacts in King County - part 2