Is the San Francisco Bay rough? What to expect on the crossing
Sometimes, mostly on windy afternoons. The Alcatraz ferry is a 12 to 15 minute ride, but NOAA's Coast Pilot says small craft advisory conditions occur nearly every day in summer in the strongest-breeze area past Alcatraz and the southern end of Angel Island. Winter storms bring the most significant seas of the year.
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Bay · Northern California · Reputation among passengers: mixed: commonly reported as uncomfortable in the wrong conditions.
- Low
- Moderate
- High
- Very high
Roughness summarises typical reported conditions for this crossing, not a forecast for any given sailing.
Funneled summer sea breeze and tidal swirls
In the Nausea Index table of the 121 sea crossings we cover, the San Francisco Bay is rated manageable, one of 81 in that band, with 40 rated higher. Full table: the roughest sea crossings, ranked.
Key facts
- The San Francisco Bay is a bay, and passenger reports place it in the moderate roughness band.
- The mechanism behind that reputation: Funneled summer sea breeze and tidal swirls.
- Conditions are reported roughest in January, February and December.
- The calmest months are usually September and October.
Why does the San Francisco Bay get rough?
In summer a sea breeze funnels through the Golden Gate, and the strongest afternoon and evening breezes blow along the route past Alcatraz and the southern end of Angel Island. Afternoon and evening winds in northern San Francisco Bay frequently reach 20 to 25 knots in summer, and sometimes 30 knots locally. Tide adds to it: the flood current causes swirls from the Golden Gate as far east as Alcatraz and Angel Islands, and in Raccoon Strait, north of Angel Island, the tidal currents have considerable velocity, with heavy rips and swirls at times. In winter, southerly winds ahead of a cold front can reach 20 knots, often 25 knots and sometimes gale force.
When is the San Francisco Bay roughest?
Spring is generally the windiest time of the year, and the stronger events sometimes approach gale force locally in northern San Francisco Bay. In summer the sea breeze follows a daily cycle: it builds from early afternoon, peaks by late afternoon into early evening, and is lightest late at night through mid morning, and gales are rare. Weather is most tranquil in September and October, systems begin to roll through in the second half of November, and the stormiest months are December, January and February.
| Roughest water in Jan | Roughest water in Feb | Roughest water in Mar | Roughest water in Apr | Roughest water in May | Roughest water in Jun | Roughest water in Jul | Roughest water in Aug | Roughest water in Sep | Roughest water in Oct | Roughest water in Nov | Roughest water in Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Rough | Rough | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed | Calm | Calm | Mixed | Rough |
Typical seasonal pattern, not a forecast. Any month can deliver a calm crossing or a bad one. Check the marine forecast for your sailing date. Select a month to see every sea and ferry crossing ranked for it.
Where to be on board
Front to back
- Bow (front)Avoid
- MidshipBest
- Stern (aft)OK
The crossing: 12 minutes to 90 minutes
Roughest stretch: The open bay off Alcatraz and Angel Island
Midship on a low deck. Summer winds are lightest from late night through mid morning, so an early sailing is the calmer ride.
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The crossings that cross it
| Route | Typical duration | What to know |
|---|---|---|
| Pier 33 to Alcatraz Island (Alcatraz City Cruises) | 12 to 15 minutes | The National Park Service gives the same 12 to 15 minutes. The Coast Pilot places flood-current swirls as far east as Alcatraz. |
| Tiburon to Angel Island (Angel Island Ferry) | 15 minutes | Crosses Raccoon Strait, where the Coast Pilot says rips and swirls are heavy at times. |
| San Francisco Bay Cruise (Blue & Gold Fleet) | 60 minutes | A sightseeing cruise that sails under the Golden Gate Bridge and around Alcatraz Island. |
| Bay Discovery Cruise (Alcatraz City Cruises) | 90 minutes | A round trip from Pier 33 that does not dock at Alcatraz. It sails under the Golden Gate Bridge weather permitting. |
What helps on this crossing
- Take a morning sailing. The Coast Pilot says summer winds are lightest from late night through mid morning, then build from early afternoon and peak by late afternoon into early evening.
- In winter, watch for a cold front. The Coast Pilot says the strongest winter winds come in the hours before the front arrives.
- Sit midship on a low deck, keep your eyes on the horizon and put your phone away. The Alcatraz ride is only 12 to 15 minutes.
For the full toolkit see the seasickness guide, or what to do once it has already started. For what the trials actually say about the oldest trick on that list, see the verdict on looking at the horizon. If the rocking follows you ashore afterwards, that is land sickness, which is normal, and it passes.
Frequently asked questions
Is San Francisco Bay rough in July?
It is windy on summer afternoons rather than rough all day. The Coast Pilot says small craft advisory conditions occur nearly every day in summer in the strongest-breeze area, with winds of 20 to 25 knots from mid afternoon through mid evening. Winds are lightest from late night through mid morning, so an early sailing is calmer.
Is San Francisco Bay rough in January?
January is one of the stormiest months. The Coast Pilot names December, January and February as the stormiest months and says winter is the season with the most significant seas. Southerly winds ahead of a cold front can reach 20 knots, often 25 knots and sometimes gale force, and there are often long tranquil spells between storms.
Is the ferry to Alcatraz rough?
It is a short ride, 12 to 15 minutes. The Coast Pilot says the flood current causes swirls from the Golden Gate as far east as Alcatraz and Angel Islands, and summer afternoon winds are strongest past Alcatraz, so a morning sailing meets lighter wind.
When is San Francisco Bay calmest?
September and October. The Coast Pilot says weather around the bay is most tranquil in September, October and November, that gales are almost nonexistent from August through October, and that wave heights are at a minimum in autumn.
Other crossings
Sources & further reading
- https://nauticalcharts.noaa.gov/publications/coast-pilot/files/cp7/CPB7_C07_WEB.pdf
- https://home.nps.gov/articles/000/alcatraz-ferries.htm
- https://alcatrazcitycruises.com/guides/escape-to-alcatraz-how-to-get-to-the-Island
- https://alcatrazcitycruises.com/tickets/bay-discovery-cruise
- https://angelislandferry.com/
- https://www.blueandgoldfleet.com/visitor-information/
- https://www.ndbc.noaa.gov/station_page.php?station=ftpc1
Sea conditions described here are typical patterns drawn from published marine and operator information as of July 2026, not a forecast: conditions on any given sailing depend on the weather that day, and any month can deliver a calm crossing or a bad one. Route and operator names are trademarks of their respective owners; Dizzout is not affiliated with or endorsed by them. Seasickness sensitivity varies from person to person; this page is informational and not medical advice.