The best times to visit San Juan Islands for ideal weather are
June 11th to September 23rd
based on average temperature and humidity from NOAA (the National Oceanic and Atmospheric Administration). Read below for more weather and travel details.
San Juan Islands Travel Guide
Other San Juan Islands Travel Info
Weather in San Juan Islands
Average temperatures in San Juan Islands vary somewhat. Considering humidity, temperatures feel cold for about half of the year and otherwise nice with a low chance of precipitation most of the year. The area is less temperate than some — in the 38th percentile for pleasant weather — compared to tourist destinations worldwide. Weeks with ideal weather are listed above. If you’re looking for the very warmest time to visit San Juan Islands, the hottest months are August, July, and then September. See average monthly temperatures below. The warmest time of year is generally mid August where highs are regularly around 75.6°F (24.2°C) with temperatures rarely dropping below 50.2°F (10.1°C) at night.
San Juan Islands Temperatures (Fahrenheit)
San Juan Islands Temperatures (Celsius)
The way we experience weather isn’t all about temperature. Higher temperatures affect us much more at higher humidity, and colder temperatures feel piercing with high winds. Our perceived temperatures factor in humidity and wind chill to better represent how hot or cold the day feels to a person.
San Juan Islands Perceived Temperature (F)
San Juan Islands Perceived Temperature (C)
Average San Juan Islands Temperatures by Month
Daily highs (averaged for the month) usually give the best indication of the weather. A significantly lower mean and low generally just means it gets colder at night.
|Month||Avg. High (°F)||Avg. Mean (°F)||Avg. Low (°F)|
|Month||Avg. High (°C)||Avg. Mean (°C)||Avg. Low (°C)|
Precipitation (Rain or Snow)
If dry weather is what you’re after, the months with the lowest chance of significant precipitation in San Juan Islands are July, August, and then June. Note that we define “significant precipitation” as .1 inches or more in this section. The lowest chance of rain or snow occurs around early to mid July. For example, on the week of July 9th there are no days of precipitation on average. By contrast, it’s most likely to rain or snow in early January with an average of 2 days of significant precipitation the week of January 1st.
When can you find snow in San Juan Islands? Weather stations report no annual snow. Please note that a value of 0 for snow in the graph below may either mean there was no snow, or that snow is unreported.
Chance of Precipitation
The graph below shows the % chance of rainy and snowy days in San Juan Islands.
Snow on the Ground
The graph below shows the average snow on the ground in San Juan Islands (in).
Average Rain and Snow by Month
|Month||Daily Chance of Rain||Average Snow Depth (in)||Total Precipitation (in)|
|Month||Daily Chance of Rain||Average Snow Depth (cm)||Total Precipitation (cm)|
Humidity and Wind
San Juan Islands has some very humid months, and above average humidity throughout the year. The least humid month is April (65.4% relative humidity), and the most humid month is January (76.8%).
Wind in San Juan Islands is usually calm. The windiest month is December, followed by November and February. December’s average wind speed of around 5.9 knots (6.8 MPH or 10.9 KPH) is considered “a light breeze.” Maximum sustained winds (the highest speed for the day lasting more than a few moments) are at their highest in mid December where average top sustained speeds reach 14.5 knots, which is considered a moderate breeze.
Relative Humidity (%)
The graph below shows the average % humidity by month in San Juan Islands.
The graph below shows wind speed (max and average) in knots.
Average Wind Speeds
Show Wind Speeds
All wind speeds are in knots. 1 knot = 1.15 MPH or 1.85 KPH.
|Month||Avg. Wind||Avg. Wind Feel||Sustained High Wind||High Wind Feel|
|Jan||4.9||Light breeze||11.3||Significant breeze|
|Feb||5||Light breeze||11.4||Significant breeze|
|Mar||4.9||Light breeze||11.5||Significant breeze|
|Apr||4.5||Light breeze||10.4||Gentle breeze|
|May||3.8||Barely noticeable||9.2||Significant breeze|
|Jun||3.9||Barely noticeable||9.3||Gentle breeze|
|Jul||3.5||Barely noticeable||9||Significant breeze|
|Aug||3.1||Barely noticeable||8.5||Gentle breeze|
|Sep||2.9||Barely noticeable||8.5||Significant breeze|
|Oct||3.5||Barely noticeable||9.3||Gentle breeze|
|Nov||5.2||Light breeze||12.4||Significant breeze|
|Dec||5.9||Light breeze||13.3||Significant breeze|
Show Relative Humidity by Month
|Month||Avg. Relative Humidity|
Is it Safe to Travel to San Juan Islands?
Our best data indicates this area is generally safe. As of Oct 07, 2019 there are no travel advisories or warnings for the United States; exercise normal security precautions. Check this page for any recent changes or regions to avoid: Travel Advice and Advisories. This advisory was last updated on Sep 23, 2019.
The Busiest and Least Crowded Months
The busiest month for tourism in San Juan Islands, WA, US is July, followed by August and April. Prices for hotels and flights will be most expensive during these months, though you can save if you purchase well in advance. Tourists are unlikely to visit San Juan Islands in November. Those willing to visit at these times will likely find it the least expensive month.
Estimated Tourism by Month
Most Popular Months to Visit
Overall San Juan Islands Travel Experience by Season
Spring (March through May)
Humidity and temperatures combine to make this season feel moderately cold. Highs range from 66.1°F (18.9°C) and 49.3°F (9.6°C) with warmer temperatures in the later months. Rain is rare with 2 to 5 days of significant precipitation per month. Spring is the second busiest for tourism, which makes it a good time for those looking for things to do.
Summer (June through August)
The middle-year months have comfortably cool weather with high temperatures that are comfortable. These months see the least precipitation with 1 to 2 days of precipitation per month. June – August is the busiest season for tourism in San Juan Islands, so lodging and other accommodations may cost more than usual.
Fall (September through November)
Fall daily highs range from 71.4°F (21.9°C) and 46.7°F (8.2°C), which will feel chilly given the humidity and wind. It rains or snows a significant amount: 4 to 7 days per month. Tourism is the slowest during these months due to the weather, so hotels may be affordably priced.
Winter (December through February)
Weather is too cold this time of year in San Juan Islands to be enjoyable for warm weather travelers. The average high during this season is between 49.8°F (9.9°C) and 44.6°F (7°C). On average, it rains or snows a fair amount: 4 to 8 times per month. These times of year are fairly slow with tourists.