Early autumn · Weather & things to do
San Juan Island in September
San Juan Island cools off: highs slip to 65°F (18°C), from 70°F in August, with lows of 54°F (12°C) and about 2.0 in (50 mm) of rain.
At 91/100 for comfort (3rd of 12), it's one of the best months to visit.
- Avg high
- 65°F (18°C)
- Avg low
- 54°F (12°C)
- Rain
- 2.0 in (50 mm)
- Humidity
- 77%
- Cloud cover
- 54%
- Daylight
- ~12 h 20 min
- Comfort score
- 91/100 · Great
What September feels like
Expect mild afternoons around 65°F (18°C), good for long walks.
Lows average 54°F (12°C).
Rain is moderate at about 2.0 in (50 mm) for the month.
Plan around September
September is one of San Juan Island's best months on the climate data.
- Last dry month before the rain picks up: October brings 4.3 in (109 mm).
- Last of the best-scoring months: by October, the score drops to 64/100.
- Comfort slips from 95/100 in August to 91/100.
- September sits inside the May – Sep window our Puget Sound Islands route recommends.
What to pack for September
- A warm layer for eveningsnights drop to 54°F
- Comfortable walking shoesmost places below are best reached on foot or with short walks
What to do in San Juan Island in September
With conditions on your side, the picks below favor time outside.
Whale watching from Friday Harbor
Boat tours to find orcas, humpbacks and minke whales in Haro Strait.
Why now Our curated notes say it's best May–Sep.
San Juan Island Brewing Company
Brewpub two blocks from the ferry with pizzas and a patio.
Why now September scores 91/100 for comfort, good conditions for being outside.
San Juan Islands Sculpture Park
Over 100 sculptures along trails at Roche Harbor.
Why now Highs near 65°F and 2.0 in of monthly rain make this an easy outdoor pick.
The Whale Museum
Small Friday Harbor museum on the Southern Resident orcas and local research.
Duck Soup
Long-running island restaurant using local produce and seafood.
Nearby in September
- Victoria in September~18 mi · highs 65°F, 2.0 in rain · similar daytime temperatures, about as wet
- Vancouver in September~52 mi · highs 68°F, 4.8 in rain · 2°C (3°F) warmer by day, wetter
- Olympic NP in September~57 mi · highs 53°F, 3.4 in rain · 6°C (11°F) cooler by day, wetter
- Bainbridge Island in September~67 mi · highs 69°F, 2.3 in rain · 3°C (5°F) warmer by day, about as wet
NASA POWER 2001–2025 monthly averages on a ~50 km grid. Comfort scores weigh temperature, rain, humidity and cloud: see how we score each month. Check a forecast before you go.
San Juan Island in September: quick answers
Is September a good time to visit San Juan Island?
Yes. On the climate data it's one of the best months, scoring 91/100. Expect highs of 65°F (18°C) and 2.0 in (50 mm) of rain. September is inside the May – Sep window our Puget Sound Islands route recommends.
How hot is San Juan Island in September?
Average highs are 65°F (18°C) and average lows 54°F (12°C), making it the 3rd-warmest month by daytime highs.
Does it rain a lot in San Juan Island in September?
Not much: about 2.0 in (50 mm) of rain falls across September on average, the 4th-driest month of the year. The annual total is about 39.0 in (991 mm).
What should I pack for San Juan Island in September?
Bring a warm layer for evenings (nights drop to 54°F) and comfortable walking shoes (most places below are best reached on foot or with short walks).
More on San Juan Island
Routes in season in September
- Puget Sound Islands May – Sep
Planning San Juan Island in September?
Plan it together in TripsCircle: one itinerary, one shared packing list and costs split as you go.