Posey Island State Park - United States

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About Posey Island State Park

RV quick facts for Posey Island State Park

DetailInformation
Road restrictionsNo road access to the island; RVs must stay at mainland or San Juan Island campgrounds and paddle in
Full hookupsNone on the island; primitive kayak-in campsites only
Dump stationNot available on the island; use facilities at Roche Harbor or other San Juan Island campgrounds
Potable waterNone on the island; bring all water needed for the trip
Cell serviceLimited; coverage varies on the water and at the island
Reservation windowCampsites managed through Washington State Parks; reservations recommended in summer
Ferry accessReach San Juan Island via Washington State Ferry from Anacortes; vehicle reservations strongly recommended
Nearest launchRoche Harbor on the north end of San Juan Island

Best time to visit Posey Island State Park

Late spring through early fall, roughly May through September, offers the calmest paddling conditions, longest daylight, and the most reliable dry weather in the San Juan Islands. July and August bring peak wildflower viewing earlier in the season and the warmest sea temperatures, though Roche Harbor and the San Juan Island ferry get busy. Shoulder months like May, June, and September balance lighter crowds with workable weather, while winter brings frequent rain, strong southerly wind storms, and challenging open-water crossings unsuitable for casual paddlers.

Jan 90 mm
45°F - 34°F

Cold, wet, and windy; open-water paddling not recommended for casual visitors

Feb 65 mm
48°F - 35°F

Winter storms common; few visitors

Mar 55 mm
51°F - 37°F

Cool and showery; early-season paddlers only

Apr 40 mm
56°F - 41°F

Wildflowers begin to appear

May 30 mm
62°F - 46°F

Drier weather and good shoulder-season paddling

Jun 25 mm
66°F - 51°F

Long daylight; popular with kayak campers

Jul 20 mm
71°F - 54°F

Peak season; book ferries and campsites well ahead

Aug 25 mm
71°F - 54°F

Warmest, driest month; busiest at Roche Harbor

Sep 35 mm
67°F - 50°F

Excellent shoulder-season window with thinner crowds

Oct 70 mm
57°F - 44°F

Rain returns; wind picks up

Nov 100 mm
49°F - 39°F

Cold, wet, and stormy; minimal visitation

Dec 100 mm
45°F - 35°F

Winter wind storms common; open-water crossings hazardous

Things to do at Posey Island State Park

  • Sea Kayaking from Roche Harbor Moderate

    Sea kayaking is the primary way to reach Posey Island, with a short crossing from Roche Harbor on the north end of San Juan Island. Paddlers can circle the island, land on its small beaches, and continue exploring nearby waters. Watch tides and currents, which can be strong in this part of the Salish Sea. nps.gov/places/posey-island-marine-state-park.htm

  • Primitive Kayak-In Camping Moderate

    Posey Island offers two primitive campsites reserved for kayak and small-boat visitors, making it a sought-after overnight destination in the San Juans. Sites have no potable water or garbage service, so visitors must pack in supplies and pack out all waste. Reservations through Washington State Parks are recommended in summer. nps.gov/places/posey-island-marine-state-park.htm

  • Wildlife and Porpoise Viewing Easy

    The waters around Posey Island are a good place to look for harbor porpoises, seals, bald eagles, and seabirds. Speiden Island, just to the north, can be observed from the water and is home to exotic animals like antelope and longhorn sheep introduced during its time as a private game reserve. Bring binoculars and keep a respectful distance from wildlife. nps.gov/places/posey-island-marine-state-park.htm

  • Wildflower Walks in Spring Easy

    In late spring, Posey Island produces seasonal wildflower displays across its small footprint. Visitors can enjoy a short walk around the island while staying on durable surfaces to protect fragile vegetation. Stick to Leave No Trace practices given the park's tiny size. nps.gov/places/posey-island-marine-state-park.htm

  • Day Trips from Roche Harbor Easy
    RV parking available

    Roche Harbor Resort serves as a popular launch point for day paddles to Posey Island and surrounding marine state parks. RVers staying on San Juan Island can park at the harbor area, rent kayaks or launch their own, and return the same day. The short distance makes it accessible for paddlers with moderate experience.

  • Photography of the Salish Sea Easy

    Posey Island offers low-elevation views across the Salish Sea toward Speiden Island, Henry Island, and the Canadian Gulf Islands. Sunrise and sunset light the waters and distant ridgelines for dramatic photos. Bring weatherproof gear, as conditions can shift quickly.

  • Exploring Nearby San Juan Island Easy
    RV parking available

    RV travelers basing on San Juan Island can pair a Posey Island paddle with visits to San Juan Island National Historical Park, Lime Kiln Point State Park for orca viewing, and Friday Harbor's shops and restaurants. These stops are all accessible by RV-friendly roads on the island. Plan ferry timing carefully when leaving the island.

Top Hosts near WA, United States

Stanislav106 trips - Joined Aug 2018Superhost

Host was very easy to work with. We got late for our drop off time but he understood our situation. We enjoyed our trip very much.

Pushpika W. - Jun 2025

Fantastic! Great to deal with and excellent vehicle

Matthew W. - Mar 2025

Mark66 trips - Joined Aug 2018Superhost

This was our first time renting a trailer and it was awesome! Mark and his wife were lovely people and it was a pleasure meeting and communicating with them. We had everything we needed in the trailer and it worked perfectly for where we were with no hookups. Anytime we had questions, Mark was very quick to answer and explained everything about the trailer before they left. Thank you so much guys! :)

Jasmyne D. - May 2026

It was my first RV experience. I used it so safely and comfortably.

EJ L. - Sep 2025

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RV Rentals Posey Island State Park

Posey Island State Park, WA, United States

How to get to Posey Island State Park

Posey Island sits about a quarter mile off Roche Harbor on the north end of San Juan Island, and the standard approach is to launch a kayak from Roche Harbor or San Juan County Park. RVers must first reach San Juan Island via the Washington State Ferry from Anacortes, roughly 80 miles and 1.5 to 2 hours north of Seattle by road plus the ferry crossing to Friday Harbor. Ferry reservations are essential for vehicles, and oversize RVs pay by length, so check vehicle size limits before booking. The nearest commercial airport for fly-and-rent travelers is Seattle-Tacoma International Airport (SEA), with smaller regional service into Friday Harbor Airport.

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