Marine Weather API for the Pacific Northwest

Marine Weather Challenges in the Pacific Northwest

The Pacific Northwest marine environment spans from the protected waters of Puget Sound to the exposed Oregon and Washington outer coasts. The contrast is extreme — calm, sheltered anchorages in the San Juan Islands can sit just a few hours from the open Pacific, where winter storms generate some of the largest seas on the planet.

The San Juan Islands offer sheltered cruising grounds, but strong tidal currents through narrow passages require precise timing. Deception Pass, Cattle Pass, and the channels between the islands see currents exceeding 6 knots that create dangerous overfalls, standing waves, and whirlpools — conditions that change hour by hour with the tide.

The Columbia River Bar is one of the most dangerous bar crossings in the world — weather conditions determine whether it's safe to cross. Known as the "Graveyard of the Pacific," the bar has claimed over 2,000 vessels. Wind direction, swell height and period, tide stage, and river flow all factor into crossing decisions.

Winter Pacific storms bring enormous seas to the outer coast, while summer brings surprisingly pleasant conditions in the inland waters. For developers building marine applications for this region, understanding the dramatic differences between inland and offshore conditions is essential.

Get a Marine Forecast for the Pacific Northwest

Here's how to get an AI-powered marine weather forecast for the San Juan Islands, WA — one of the most popular cruising destinations in the Pacific Northwest:

curl -X POST https://api.sealegs.ai/v3/spotcast \
  -H "X-API-Key: your_api_key" \
  -d '{
    "latitude": 48.5126,
    "longitude": -123.0124,
    "start_date": "2026-07-18",
    "num_days": 3,
    "vessel_info": {
      "type": "sailing",
      "length_ft": 34
    }
  }'

{
  "summary": "Good three-day window for a 34ft sailing vessel
    in the San Juan Islands. Friday shows west-northwest winds
    10-14kt — a typical summer afternoon sea breeze. Seas 1-2ft
    in the channels with moderate tidal currents. Current flood
    tide through Cattle Pass creating mild overfalls. Excellent
    conditions for island-hopping. Saturday similar with lighter
    morning winds building in the afternoon. Sunday may see fog
    developing after sunset — monitor visibility if planning
    evening passages.",
  "daily_forecasts": [
    {
      "date": "2026-07-18",
      "classification": "Excellent",
      "confidence": 0.91,
      "wind_speed_kt": 12,
      "wind_gust_kt": 16,
      "wave_height_ft": 1.5,
      "wave_period_s": 3
    }
  ]
}

The same request works for any Pacific Northwest coordinates. Use 47.6062, -122.3321 for Seattle / Elliott Bay, 46.2550, -124.0580 for the Columbia River Bar, or 44.6368, -124.0535 for Newport, OR.

Key Weather Parameters for the Pacific Northwest

The API returns a full set of marine weather parameters. For Pacific Northwest waters, these are especially important:

• Wind speed & direction — Gale warnings are common in winter on the outer coast; summer sea breezes in the islands are more manageable but still require attention
• Wave height & period — Pacific swell on the outer coast has a 10-15 second period and can be massive, while wind chop in Puget Sound runs 2-4 seconds
• Tidal currents — Critical for passage planning through narrows, passes, and straits where current can exceed 6 knots
• Visibility — Summer fog along the outer coast can persist for days, and winter rain squalls reduce visibility in the inland waters
• Swell — Long-period Pacific swell wraps around the coast and is especially important for bar crossings where swell interacts with outgoing current
• AI classification — The daily GO / CAUTION / NO-GO rating accounts for how all parameters interact for your vessel type

Use Cases in the Pacific Northwest

Popular Pacific Northwest Coordinates

Here are commonly used coordinates for Pacific Northwest marine forecasts:

• San Juan Islands, WA — 48.5126, -123.0124
• Seattle / Elliott Bay — 47.6062, -122.3321
• Strait of Juan de Fuca — 48.3813, -124.0620
• Columbia River Bar, OR — 46.2550, -124.0580
• Astoria, OR — 46.1879, -123.8313
• Newport, OR — 44.6368, -124.0535
• Victoria, BC (nearby) — 48.4284, -123.3656