The weather on San Juan Island is extremely variable. Visitors should come prepared for a wide range of conditions. Rain gear and layered clothing are essential.
Overall, the San Juan Archipelago has a moderate marine climate with pleasant summers and mild, wet winters.
Summers tend to be fair and warm, with high temperatures between 65 and 75 degrees F. July, August and September are the driest months, with heavier precipitation during the rest of the year.
While winters are mild at lower elevation, with temperatures in the 30's and 40's, snowfall can be heavy during some winter storms.
At any time of year, visitors should come prepared for a variety of conditions. The Seattle office of the National Weather Service provides up-to-date weather information and forecasts.