Average Weather in Vashon Washington, United States
In Vashon, the summers are short, warm, dry, and partly cloudy and the winters are very cold, wet, and mostly cloudy. Over the course of the year, the temperature typically varies from 37°F to 78°F and is rarely below 29°F or above 88°F.
Based on the tourism score, the best time of year to visit Vashon for warm-weather activities is from early July to late August.
The warm season lasts for 2.7 months, from June 22 to September 12, with an average daily high temperature above 72°F. The hottest day of the year is August 2, with an average high of 78°F and low of 57°F.
The cool season lasts for 3.6 months, from November 11 to February 28, with an average daily high temperature below 52°F. The coldest day of the year is December 22, with an average low of 37°F and high of 45°F.
Average High and Low Temperature
Average Hourly Temperature
In Vashon, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.
The clearer part of the year in Vashon begins around June 12 and lasts for 3.8 months, ending around October 7. On August 2, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 75% of the time, and overcast or mostly cloudy 25% of the time.
The cloudier part of the year begins around October 7 and lasts for 8.2 months, ending around June 12. On January 19, the cloudiest day of the year, the sky is overcast or mostly cloudy 72% of the time, and clear, mostly clear, or partly cloudy 28% of the time.
Cloud Cover Categories
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Vashon varies significantly throughout the year.
The wetter season lasts 6.7 months, from October 9 to April 30, with a greater than 31% chance of a given day being a wet day. The chance of a wet day peaks at 55% on November 17.
The drier season lasts 5.3 months, from April 30 to October 9. The smallest chance of a wet day is 7% on August 2.
Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 54% on November 17.
Daily Chance of Precipitation
To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Vashon experiences extreme seasonal variation in monthly rainfall.
Rain falls throughout the year in Vashon. The most rain falls during the 31 days centered around November 22, with an average total accumulation of 7.2 inches.
The least rain falls around July 28, with an average total accumulation of 0.5 inches.
Average Monthly Rainfall
The sliding 31-day liquid-equivalent quantity of snowfall in Vashon does not vary significantly over the course of the year, staying within 0.1 inches of 0.1 inches throughout.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Vashon varies significantly over the course of the year. In 2020, the shortest day is December 21, with 8 hours, 27 minutes of daylight; the longest day is June 20, with 15 hours, 58 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:12 AM on June 15, and the latest sunrise is 2 hours, 45 minutes later at 7:57 AM on December 31. The earliest sunset is at 4:18 PM on December 10, and the latest sunset is 4 hours, 52 minutes later at 9:11 PM on June 25.
Daylight saving time (DST) is observed in Vashon during 2020, starting in the spring on March 8, lasting 7.8 months, and ending in the fall on November 1.
Sunrise & Sunset with Twilight and Daylight Saving Time
The perceived humidity level in Vashon, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, remaining a virtually constant 0% throughout.
Humidity Comfort Levels
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed in Vashon experiences mild seasonal variation over the course of the year.
The windier part of the year lasts for 6.4 months, from October 13 to April 25, with average wind speeds of more than 4.4 miles per hour. The windiest day of the year is November 29, with an average hourly wind speed of 5.6 miles per hour.
The calmer time of year lasts for 5.6 months, from April 25 to October 13. The calmest day of the year is August 1, with an average hourly wind speed of 3.2 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Vashon varies throughout the year.
The wind is most often from the north for 2.2 months, from July 14 to September 21, with a peak percentage of 44% on August 4. The wind is most often from the south for 9.8 months, from September 21 to July 14, with a peak percentage of 63% on January 1.
Vashon 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 water temperature experiences some seasonal variation over the course of the year.
The time of year with warmer water lasts for 3.1 months, from June 23 to September 28, with an average temperature above 55°F. The day of the year with the warmest water is August 19, with an average temperature of 57°F.
The time of year with cooler water lasts for 4.0 months, from December 10 to April 10, with an average temperature below 49°F. The day of the year with the coolest water is February 11, with an average temperature of 47°F.
Average Water Temperature
Best Time of Year to Visit
To characterize how pleasant the weather is in Vashon throughout the year, we compute two travel scores.
The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Vashon for general outdoor tourist activities is from early July to late August, with a peak score in the first week of August.
The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Vashon for hot-weather activities is from mid July to mid August, with a peak score in the first week of August.
The growing season in Vashon typically lasts for 9.2 months (279 days), from around February 23 to around November 28, rarely starting before January 20 or after March 16, and rarely ending before November 6 or after December 19.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms in Vashon should appear around April 16, only rarely appearing before March 28 or after May 5.
Growing Degree Days
The average daily incident shortwave solar energy experiences extreme seasonal variation over the course of the year.
The brighter period of the year lasts for 3.3 months, from May 12 to August 23, with an average daily incident shortwave energy per square meter above 5.6 kWh. The brightest day of the year is July 20, with an average of 6.8 kWh.
The darker period of the year lasts for 3.8 months, from October 25 to February 18, with an average daily incident shortwave energy per square meter below 2.1 kWh. The darkest day of the year is December 25, with an average of 0.9 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Vashon are 47.447 deg latitude, -122.460 deg longitude, and 131 ft elevation.
The topography within 2 miles of Vashon contains only modest variations in elevation, with a maximum elevation change of 456 feet and an average elevation above sea level of 258 feet. Within 10 miles contains only modest variations in elevation (522 feet). Within 50 miles contains significant variations in elevation (9,045 feet).
The area within 2 miles of Vashon is covered by trees (52%), water (26%), and artificial surfaces (20%), within 10 miles by water (38%) and artificial surfaces (31%), and within 50 miles by trees (53%) and artificial surfaces (14%).
This report illustrates the typical weather in Vashon, 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
There are 3 weather stations near enough to contribute to our estimation of the temperature and dew point in Vashon.
For each station, the records are corrected for the elevation difference between that station and Vashon according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
The estimated value at Vashon is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Vashon and a given station.
The stations contributing to this reconstruction are: Seattle-Tacoma International Airport (55%, 11 kilometers, east); Tacoma Narrows Airport (25%, 22 kilometers, southwest); and Bremerton National Airport (20%, 23 kilometers, west).
Time zones for aiports and weather stations are provided by AskGeo.com .