Weather in the San Juan Islands

The San Juan Islands enjoy a sub-oceanic climate with mild, rainy winters and warm, sunny summers.

The islands are relatively untouched by humidity due to their geographical location near the Olympic Mountains but do receive around 40 inches of rain per year. Most of this rainfall usually occurs in winter (December to February). 

While the weather in winter is considered mild, temperatures can still drop to freezing levels (especially at night). However, temperatures aren't often low enough for snowfall on the main islands. The island that is the most likely to receive snow is Lopez Island.

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 warm enough to enjoy lengthy periods outside. Average temperatures hover in the low 20s but can drop in the evenings, so bring a cardigan or light jacket. You'll also enjoy more hours of daylight from June through August.

June to September sees minimal rainfall, allowing you to maximise the many activities on offer.

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 higher prices for transportation and accommodation. If you want to avoid sharing the islands with a whole heap of other travellers, consider April, May, September or October as the weather is still fairly warm and dry.

You'll also have a great chance of spotting killer whales and orcas from May to October, so make sure you factor that in when deciding when to visit.

Average temperatures in the San Juan Islands 


Average high

Average low

March to May



June to August



September to November



December to February



Want to learn more about the San Juan Islands? Return to San Juan Islands FAQs

Our San Juan Islands trips

Get inspired on The Good Times