is seattle humid or dry

Is Seattle humid or dry? If you are going to visit Seattle for the first time or contemplating living there, it is natural to ask about its climate.

And that is precisely when you are likely to ask, “Is Seattle dry or humid?” If you check the list, Seattle is definitely among the most humid cities in the US.

But, does it really feel humid?

Considering its geographical location, and the impact of water bodies, you are right to question, “Is Seattle’s summer humid or dry?” So, what do you think?

Seattle’s humidity levels are typically moderate in comparison to other cities across the US, but the humidity levels can fluctuate depending on the season.   

Is Seattle Humid or Dry?

humidity levels in seattle

Seattle is definitely more on the humid side, but you can call it “moderately humid” through most seasons.

It is interesting to note that Seattle experiences relatively consistent levels of humidity throughout the year.

The average humidity remains around 66% during the summer months and 79% during the winter months.

So many people visiting the area for the first time hope to experience a more significant contrast, given the higher precipitation rate in Seattle throughout the winter season, but that is not the case. 

Factors Affecting Humidity in Seattle

factors affecting humidity in seattle

The moderately humid Seattle is actually the result of many different factors, such as the following: 

Proximity to the Pacific Ocean

The humidity levels in Seattle are greatly influenced by its close proximity to the Pacific Ocean.

Humidity in the air is partly caused by the ocean, which serves as a source of moisture.

Humidity levels in the city are influenced by the moisture-laden air masses carried by the prevailing westerly winds from the ocean. 

Moderating Effect on Temperature

moderating effect on temperature

In general, Seattle’s temperature and humidity are regulated by the Pacific Ocean.

Coastal areas tend to have cooler summers and milder winters in comparison to inland regions.

What’s more, the sea’s impact helps keep the humidity levels consistent and mild all year round. 

Marine Layer and Fog

Seattle often experiences the marine layer, particularly in the summer season.

The formation process occurs when the cool and damp air from the ocean moves over the frigid waters near the shore, resulting in the creation of low-lying clouds and fog.

The presence of this oceanic layer may lead to increased moisture levels, especially during the early hours and in the regions near the coast. 

Air Masses and Weather Systems

air masses and weather systems

Air masses significantly influence Seattle’s weather and humidity levels.

As the Pacific Ocean air masses travel towards the interior, they bring along moisture, which affects the humidity levels of the area.

The source and attributes of these air masses may impact the level of dampness and consequent moisture in the atmosphere. 

Onshore and Offshore Flow

onshore and offshore flow

Air movement from the ocean towards the land is known as onshore flow, which results in increased humidity levels.

On the other hand, the offshore flow is characterized by the movement of air from the land towards the sea, leading to less humid weather.

Seattle’s humidity levels can be influenced by the direction and intensity of onshore and offshore flows, which are in turn determined by the prevailing wind patterns and weather systems. 

Weather Patterns and Humidity

Various weather systems can affect Seattle’s humidity levels, including low-pressure systems and frontal boundaries.

Fluctuations in humidity can occur when these systems come into contact with the area, as they have the ability to either increase or decrease moisture transportation.

Humidity levels in the short-term can be affected by precipitation that comes with different weather patterns. 

Local Geography

local geography

The local geography of Seattle has a role to play in determining the humidity levels in the area.

Here is a bit more about how factors like water bodies, wind patterns, and topography change humidity in Seattle:

Effect of Water Bodies

Humidity levels in Seattle may be impacted by the presence of water bodies such as Puget Sound and Lake Washington in the local geography.

effect of water bodies

The vast water bodies have the potential to function as sources of moisture, emitting moisture into the atmosphere by means of evaporation.

Fact: The presence of water bodies in Seattle can lead to increased humidity levels, particularly in regions close to them. 

Topography and Wind Patterns

Humidity levels are impacted by wind patterns and airflow, which are in turn influenced by the topography and terrain of the area.

The presence of mountains and valleys can cause changes in wind speed and direction, which can affect the movement and blending of moisture.

topography and wind patterns

Seattle’s diverse topography can cause distinct fluctuations in humidity levels, resulting in the formation of microclimates throughout the city.

Fact: The humidity levels in Seattle vary due to the city's diverse geography and microclimates and the levels can vary in different parts of the city. 

Seasonal Variations in Humidity Levels in Seattle

seasonal variations in humidity levels in seattle

An interesting thing to know about the climate in Seattle is how it changes through different seasons.

The Pacific Ocean’s moderating effect makes Seattle’s summers less humid than other areas.

Although the humidity level is usually low, there may be times when it increases, particularly in the mornings or after it has rained.

Seattle experiences a lot of rain during the winter season, which adds to the humidity levels in the air.

Although the humidity levels may not be as high as in tropical regions, the rainy season can cause an increase in humidity compared to the drier summer months.

Transition Seasons

transition seasons

Seattle undergoes transitional weather patterns during the spring and fall seasons.

Humidity levels can vary due to the changing weather systems and air masses that occur during these seasons.

Fact: During the spring season, there is a possibility of higher humidity levels in Seattle due to the interaction between warm air masses and the cooler waters of the Pacific Ocean. 

Do Humans Have an Impact on Humidity in Seattle?

human impact on seattle's humidity

Human activities have a definite role to play in determining how humid or dry Seattle is.

For instance, Seattle’s humidity levels can be affected by the heat island effect caused by the urban environment.

Metropolitan regions usually experience elevated temperatures, leading to increased evaporation and subsequent humidity levels.

Urban areas may experience localized increases in humidity due to the prevalence of concrete, asphalt, and limited green spaces.

Seattle’s climate and humidity levels are anticipated to be greatly impacted by climate change.

Studying and monitoring these changes is essential to better understand how they impact the humidity levels in Seattle. 

An Important Consideration

Urban areas can benefit from green spaces like parks and gardens as they can help reduce humidity levels by promoting cooling effects and evapotranspiration.

Vegetation plays a crucial role in maintaining the humidity levels in the city as it releases moisture into the air, thereby creating a pleasant microclimate.

Fact: In the future, humidity levels may be affected by the changes in precipitation patterns and the increase in temperatures 

Does Seattle Really Feel Humid?

does seattle really feel humid

If you were to discover that Seattle is on the list of the most humid cities in the US, you might assume that the air in Seattle is rather damp, correct?

If you have visited this place before, you can attest that this statement is inaccurate.

And it is different because of the correlation between the dew point and temperature.

The temperature refers to the amount of heat present in the air, whereas the dew point is the particular temperature needed for full humidity.  

The level of comfort you experience is determined by the dew point

An Important Consideration

Humidity levels are inversely proportional to the difference between dew point and temperature.

If the difference is large, humidity is low, and if the difference is small, humidity is high.

humidity levels are inversely proportional

Suppose the dew point in Seattle is approximately 55, and the temperature is around 60C; in that case, you will encounter more humidity than when the dew point is about 55 with a temperature around 80C. 


Is Seattle humid or dry? Seattle is among the most humid cities in the US, but it is certainly not at the top of the list.

In fact, the humidity here is rather moderate, and many other factors play a role in making it feel a bit less humid as compared to many other cities with similar humidity levels.

Learning about these seasonal changes in humidity can help us understand a lot about how to keep the effects of global warming in check.