1. WeatherSpark.com
  2. United States
  3. Washington
  4. Seattle-Tacoma International Airport

Summer Weather at Seattle-Tacoma International Airport Washington, United States

Daily high temperatures increase by 7°F, from 68°F to 75°F, rarely falling below 59°F or exceeding 89°F. The highest daily average high temperature is 78°F on August 2.

Daily low temperatures increase by 4°F, from 51°F to 56°F, rarely falling below 47°F or exceeding 62°F. The highest daily average low temperature is 58°F on August 2.

For reference, on August 2, the hottest day of the year, temperatures at Seattle-Tacoma International Airport typically range from 58°F to 78°F, while on December 22, the coldest day of the year, they range from 37°F to 45°F.

Average High and Low Temperature in the Summer at Seattle-Tacoma International Airport

Average High and Low Temperature in the Summer at Seattle-Tacoma International AirportJunJulAug40°F40°F45°F45°F50°F50°F55°F55°F60°F60°F65°F65°F70°F70°F75°F75°F80°F80°F85°F85°F90°F90°FSpringFallAug 278°FAug 278°F58°F58°FJun 168°FJun 168°F51°F51°FAug 3175°FAug 3175°F56°F56°FJul 174°FJul 174°F55°F55°F
The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the hourly average summer temperatures. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature in the Summer at Seattle-Tacoma International Airport

Average Hourly Temperature in the Summer at Seattle-Tacoma International AirportJunJulAug12 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMSpringFallcoldcoldcoldcoolcomfortablewarm
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The average hourly temperature, color coded into bands. The shaded overlays indicate night and civil twilight.

Paris, France (5,011 miles away) is the far-away foreign place with temperatures most similar to Seattle-Tacoma International Airport (view comparison).

Map
Marker
© OpenStreetMap contributors

Compare Seattle-Tacoma International Airport to another city:

Map

The summer at Seattle-Tacoma International Airport experiences very rapidly decreasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy decreasing from 54% to 34%. The lowest chance of overcast or mostly cloudy conditions is 25% on August 2.

The clearest day of the summer is August 2, with clear, mostly clear, or partly cloudy conditions 75% of the time.

For reference, on January 19, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 73%, while on August 2, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 75%.

Cloud Cover Categories in the Summer at Seattle-Tacoma International Airport

Cloud Cover Categories in the Summer at Seattle-Tacoma International AirportJunJulAug0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%SpringFallJan 1927%Jan 1927%Jun 146%Jun 146%Aug 3166%Aug 3166%Jul 161%Jul 161%Aug 175%Aug 175%clearmostly clearpartly cloudymostly cloudyovercast
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. At Seattle-Tacoma International Airport, the chance of a wet day over the course of the summer is very rapidly decreasing, starting the season at 29% and ending it at 16%.

For reference, the year's highest daily chance of a wet day is 57% on November 17, and its lowest chance is 8% on August 10.

Probability of Precipitation in the Summer at Seattle-Tacoma International Airport

Probability of Precipitation in the Summer at Seattle-Tacoma International AirportJunJulAug0%0%5%5%10%10%15%15%20%20%25%25%30%30%35%35%SpringFallAug 38%Aug 38%Jun 129%Jun 129%Aug 3116%Aug 3116%Jul 117%Jul 117%rain
The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the season and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during the summer at Seattle-Tacoma International Airport is decreasing, starting the season at 2.0 inches, when it rarely exceeds 3.4 inches or falls below 0.6 inches, and ending the season at 1.3 inches, when it rarely exceeds 2.9 inches or falls below 0.1 inches.

The lowest average 31-day accumulation is 0.6 inches on July 29.

Average Monthly Rainfall in the Summer at Seattle-Tacoma International Airport

Average Monthly Rainfall in the Summer at Seattle-Tacoma International AirportJunJulAug0 in0 in1 in1 in2 in2 in3 in3 in4 in4 in5 in5 inSpringFallJul 280.6 inJul 280.6 inJun 12.0 inJun 12.0 inAug 311.3 inAug 311.3 inJul 11.1 inJul 11.1 in
The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average snowfall.

Over the course of the summer at Seattle-Tacoma International Airport, the length of the day is very rapidly decreasing. From the start to the end of the season, the length of the day decreases by 2 hours, 21 minutes, implying an average daily decrease of 1 minute, 33 seconds, and weekly decrease of 10 minutes, 50 seconds.

The shortest day of the summer is August 31, with 13 hours, 22 minutes of daylight and the longest day is June 20, with 15 hours, 58 minutes of daylight.

Hours of Daylight and Twilight in the Summer at Seattle-Tacoma International Airport

Hours of Daylight and Twilight in the Summer at Seattle-Tacoma International AirportJunJulAug0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hrSpringFallJun 2015 hr, 58 minJun 2015 hr, 58 minnightnightdaydayAug 3113 hr, 22 minAug 3113 hr, 22 minAug 114 hr, 54 minAug 114 hr, 54 min
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise of the summer at Seattle-Tacoma International Airport is 5:11 AM on June 15 and the latest sunrise is 1 hour, 16 minutes later at 6:27 AM on August 31.

The latest sunset is 9:10 PM on June 24 and the earliest sunset is 1 hour, 20 minutes earlier at 7:50 PM on August 31.

Daylight saving time is observed at Seattle-Tacoma International Airport during 2024, but it neither starts nor ends during the summer, so the entire season is in daylight saving time.

For reference, on June 20, the longest day of the year, the Sun rises at 5:12 AM and sets 15 hours, 58 minutes later, at 9:09 PM, while on December 21, the shortest day of the year, it rises at 7:54 AM and sets 8 hours, 27 minutes later, at 4:21 PM.

Sunrise & Sunset with Twilight in the Summer at Seattle-Tacoma International Airport

Sunrise & Sunset with Twilight in the Summer at Seattle-Tacoma International AirportJunJulAug2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMSpringFall5:11 AM5:11 AMJun 159:08 PMJun 159:08 PM6:27 AM6:27 AMAug 317:50 PMAug 317:50 PM5:16 AM5:16 AMJul 19:09 PMJul 19:09 PM5:48 AM5:48 AMAug 18:42 PMAug 18:42 PMSolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day in the summer. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.

Solar Elevation and Azimuth in the Summer at Seattle-Tacoma International Airport

Solar Elevation and Azimuth in the Summer at Seattle-Tacoma International AirportJunJulAug12 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMSpringFall00102020303040506000101020303040405060
northeastsouthwest
Solar elevation and azimuth in the the summer of 2024. The black lines are lines of constant solar elevation (the angle of the sun above the horizon, in degrees). The background color fills indicate the azimuth (the compass bearing) of the sun. The lightly tinted areas at the boundaries of the cardinal compass points indicate the implied intermediate directions (northeast, southeast, southwest, and northwest).

The figure below presents a compact representation of key lunar data for the summer of 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.

Moon Rise, Set & Phases in the Summer at Seattle-Tacoma International Airport

Moon Rise, Set & Phases in the Summer at Seattle-Tacoma International AirportJunJulAug12 AM12 AM4 AM4 AM8 AM8 AM12 PM12 PM4 PM4 PM8 PM8 PM12 AM12 AMSpringFallMay 78:23 PMMay 78:23 PMMay 236:54 AMMay 236:54 AMJun 65:38 AMJun 65:38 AMJun 216:09 PMJun 216:09 PMJul 53:58 PMJul 53:58 PMJul 213:18 AMJul 213:18 AMAug 44:14 AMAug 44:14 AMAug 1911:26 AMAug 1911:26 AMSep 26:56 PMSep 26:56 PMSep 177:35 PMSep 177:35 PM5:14 AM5:14 AM8:36 PM8:36 PM8:31 PM8:31 PM5:01 AM5:01 AM4:48 AM4:48 AM10:08 PM10:08 PM9:44 PM9:44 PM5:15 AM5:15 AM9:45 PM9:45 PM9:12 PM9:12 PM5:25 AM5:25 AM9:14 PM9:14 PM8:12 PM8:12 PM5:47 AM5:47 AM7:54 PM7:54 PM7:16 PM7:16 PM7:34 AM7:34 AM
The time in which the moon is above the horizon (light blue area), with new moons (dark gray lines) and full moons (blue lines) indicated. The shaded overlays indicate night and civil twilight.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The chance that a given day will be muggy at Seattle-Tacoma International Airport is essentially constant during the summer, remaining around 0% throughout.

For reference, on August 3, the muggiest day of the year, there are muggy conditions 0% of the time, while on January 1, the least muggy day of the year, there are muggy conditions 0% of the time.

Humidity Comfort Levels in the Summer at Seattle-Tacoma International Airport

Humidity Comfort Levels in the Summer at Seattle-Tacoma International AirportJunJulAug0%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%SpringFallAug 70%Aug 70%Jun 160%Jun 160%Jun 10%Jun 10%Aug 310%Aug 310%Jul 10%Jul 10%comfortablecomfortabledrydryhumidhumid
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The percentage of time spent at various humidity comfort levels, categorized by dew point.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed at Seattle-Tacoma International Airport is essentially constant during the summer, remaining within 0.3 miles per hour of 3.3 miles per hour throughout.

For reference, on November 30, the windiest day of the year, the daily average wind speed is 5.4 miles per hour, while on August 1, the calmest day of the year, the daily average wind speed is 3.0 miles per hour.

The lowest daily average wind speed during the summer is 3.0 miles per hour on August 1.

Average Wind Speed in the Summer at Seattle-Tacoma International Airport

Average Wind Speed in the Summer at Seattle-Tacoma International AirportJunJulAug0 mph0 mph1 mph1 mph2 mph2 mph3 mph3 mph4 mph4 mph5 mph5 mph6 mph6 mphSpringFallAug 13.0 mphAug 13.0 mphJun 13.6 mphJun 13.6 mphAug 313.3 mphAug 313.3 mphJul 13.2 mphJul 13.2 mph
The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The wind direction at Seattle-Tacoma International Airport during the summer is predominantly out of the south from June 1 to July 7 and the north from July 7 to August 31.

Wind Direction in the Summer at Seattle-Tacoma International Airport

Wind Direction in the Summer at Seattle-Tacoma International AirportSNSJunJulAug0%100%20%80%40%60%60%40%80%20%100%0%SpringFallwestsouthnortheast
northeastsouthwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions, excluding hours in which the mean wind speed is less than 1.0 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Seattle-Tacoma International Airport is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average surface water temperature at Seattle-Tacoma International Airport is gradually increasing during the summer, rising by 4°F, from 53°F to 57°F, over the course of the season.

The highest average surface water temperature during the summer is 57°F on August 21.

Average Water Temperature in the Summer at Seattle-Tacoma International Airport

Average Water Temperature in the Summer at Seattle-Tacoma International AirportJunJulAug48°F48°F50°F50°F52°F52°F54°F54°F56°F56°F58°F58°F60°F60°FSpringFallAug 2157°FAug 2157°FJun 153°FJun 153°FJul 155°FJul 155°FAug 156°FAug 156°F
The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season at Seattle-Tacoma International Airport typically lasts for 9.1 months (279 days), from around February 22 to around November 27, rarely starting before January 23 or after March 16, and rarely ending before November 3 or after December 20.

The summer at Seattle-Tacoma International Airport is reliably fully within the growing season.

Time Spent in Various Temperature Bands and the Growing Season in the Summer at Seattle-Tacoma International Airport

Time Spent in Various Temperature Bands and the Growing Season in the Summer at Seattle-Tacoma International Airportgrowing seasongrowing seasongrowing seasonJunJulAug0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%SpringFall100%Jul 17100%Jul 17coldcoolcomfortablewarmvery cold
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The percentage of time spent in various temperature bands. The black line is the percentage chance that a given day is within the growing season.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

The average accumulated growing degree days at Seattle-Tacoma International Airport are very rapidly increasing during the summer, increasing by 1,252°F, from 346°F to 1,598°F, over the course of the season.

Growing Degree Days in the Summer at Seattle-Tacoma International Airport

Growing Degree Days in the Summer at Seattle-Tacoma International AirportJunJulAug400°F400°F600°F600°F800°F800°F1,000°F1,000°F1,200°F1,200°F1,400°F1,400°F1,600°F1,600°F1,800°F1,800°FSpringFallJun 1346°FJun 1346°FAug 311,598°FAug 311,598°FJul 1664°FJul 1664°FAug 11,134°FAug 11,134°F
The average growing degree days accumulated over the course of the summer, with 25th to 75th and 10th to 90th percentile bands.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy at Seattle-Tacoma International Airport is gradually decreasing during the summer, falling by 0.7 kWh, from 5.9 kWh to 5.2 kWh, over the course of the season.

The highest average daily incident shortwave solar energy during the summer is 6.8 kWh on July 20.

Average Daily Incident Shortwave Solar Energy in the Summer at Seattle-Tacoma International Airport

Average Daily Incident Shortwave Solar Energy in the Summer at Seattle-Tacoma International AirportJunJulAug0 kWh0 kWh1 kWh1 kWh2 kWh2 kWh3 kWh3 kWh4 kWh4 kWh5 kWh5 kWh6 kWh6 kWh7 kWh7 kWh8 kWh8 kWh9 kWh9 kWhSpringFallJul 206.8 kWhJul 206.8 kWhJun 15.9 kWhJun 15.9 kWhAug 315.2 kWhAug 315.2 kWhJul 16.6 kWhJul 16.6 kWh
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

For the purposes of this report, the geographical coordinates of Seattle-Tacoma International Airport are 47.449 deg latitude, -122.309 deg longitude, and 397 ft elevation.

The topography within 2 miles of Seattle-Tacoma International Airport contains only modest variations in elevation, with a maximum elevation change of 469 feet and an average elevation above sea level of 341 feet. Within 10 miles contains only modest variations in elevation (1,109 feet). Within 50 miles contains very significant variations in elevation (14,360 feet).

The area within 2 miles of Seattle-Tacoma International Airport is covered by artificial surfaces (99%), within 10 miles by artificial surfaces (55%) and water (28%), and within 50 miles by trees (53%) and artificial surfaces (14%).

This report illustrates the typical weather at Seattle-Tacoma International Airport, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Temperature and Dew Point

Seattle-Tacoma International Airport has a weather station that reported reliably enough during the analysis period that we have included it in our network. When available, historical temperature and dew point measurements are taken directly from this weather station. These records are obtained from NOAA's Integrated Surface Hourly data set, falling back on ICAO METAR records as required.

In the case of missing or erroneous measurements from this station, we fall back on records from nearby stations, adjusted according to typical seasonal and diurnal intra-station differences. For a given day of the year and hour of the day, the fallback station is selected to minimize the prediction error over the years for which there are measurements for both stations.

The stations on which we may fall back include but are not limited to King County International Airport, Renton Municipal Airport, Tacoma Narrows Airport, McChord Field Airport (Joint Base Lewis-McChord), Pierce County Airport Thun Field, Madigan Hospital Heliport, Bremerton National Airport, and Snohomish County Airport (Paine Field).

Other Data

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , by Jean Meeus.

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.

Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.

Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .

Time zones for airports and weather stations are provided by AskGeo.com .

Maps are © OpenStreetMap contributors.

Disclaimer

The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.

We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.

We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.

Please review our full terms contained on our Terms of Service page.