San Juan Islands weather 

The San Juan Islands enjoys a sub-oceanic climate meaning winters are often mild and rainy while summers remain sunny and warm. The islands are relatively untouched by humidity due to their geographical location near the Olympic Mountains but do receive around 40 inches per year. The majority of this rainfall usually occurs during the winter months (December, January, and February) but can also fall during the other seasons as well. 

While the weather in winter is considered mild, temperatures can still reach freezing levels (especially at night) with lows recorded at 18°F, however, temperatures as low as these aren't often enough to generate regular snowfall on the main islands. The island that is the most likely to receive snow is Lopez Island but even then the average is around 6.7 inches. 

What's the summer weather like in the San Juan Islands? 

Summer is one of the best times to visit the San Juan Islands as the weather is fairly mild but still warm enough to enjoy spending a lengthy period of time outside. Average temperatures hover around the 70°Fs but can lower in the evenings so make sure you're still bringing cold weather-appropriate clothing such as a cardigan or light jacket. During the months of June, July, and August, you'll enjoy more hours of sunlight and this might help the temperature feel warmer for longer. 

Luckily, the months from June to September see a minimal amount of rainfall, allowing you to enjoy the nice weather in peace. Precipitation isn't always a bad thing though as it keeps the foliage throughout the region's stunning landscapes and national parks lush and vibrant during the warmer weather. 

When's the best time to visit the San Juan Islands? 

Summer is the best time to visit the San Juan Islands weather-wise but you can expect larger crowds and slightly raised transportation and accommodation prices. If you want to avoid sharing the islands with a whole heap of other travelers, try journeying to the coastal destination in either April to May or September to October as the weather is still fairly warm and rainfall is relatively minimal. 

You'll also have a great chance of spotting some killer whales and orcas from May to October so make sure you factor that in when deciding the best time to travel to the islands. 

Average temperatures in the San Juan Islands 




March to May



June to August



September to November



December to February




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