San Mateo County · Año Nuevo
Año Nuevo State Park
Low Point · Reserve · Guided Access Required for Point
⚠ Data may be stale — showing last known reading. Conditions may have changed.
Wave Height
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feet
Swell Period
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seconds
Direction
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swell from
Water Temp
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°F
NOAA Buoy 46012 — Half Moon Bay
Long-period swell is dangerous. Any swell period above 15 seconds means waves are arriving in sets with long quiet intervals — sometimes 20 minutes of calm. During the quiet, energy is building offshore. People who walk to the water's edge during the lull are swept in when a set arrives.
Known Hazards
Long-Period Swell & Set Waves
Read the table above. Any swell period above 15 seconds means danger. Waves travel in sets separated by long, quiet intervals — sometimes as long as 20 minutes of calm. On long period days, stay aware! During the quiet periods between sets, energy is building offshore. People who walk to the water's edge during the lull are swept in when a set arrives.
Source: NPS / SF Fire Dept / NOAA — Joint Coastal Safety Advisory (sf-fire.org); NOAA National Weather Service Beach Hazards guidance
Low-Lying Point — Waves Sweep the Land
Año Nuevo Point sits barely above sea level. On long-period swell days, waves sweep across the entire point. There is no high ground to retreat to. Stay on designated paths only.
Source: California State Parks — Año Nuevo State Park (parks.ca.gov)
Restricted Access — Natural Preserve
The Año Nuevo Coast Natural Preserve is restricted year-round. Dec 15–Mar 31 (breeding season): access requires a reserved, docent-guided walk — no exceptions. Dec 1–14: the preserve is closed entirely. Apr 1–Nov 30: self-guided hiking permitted with a free same-day Visitor Permit from the entrance station (8:30am–3:30pm). Elephant seals are wild animals and bite. Never approach within 25 feet.
Source: California State Parks — Año Nuevo Seal Viewing Seasons (parks.ca.gov)
Cold Water — Year Round
Pacific water along this coast runs cold year round. Hypothermia can set in quickly.
Source: California State Parks — Ocean Safety (parks.ca.gov/OceanSafety); NOAA / NPS GGNRA Joint Coastal Safety Advisory
No Year-Round Lifeguard Posted
CA State Parks lifeguards patrol state beaches. There is no year-round posted lifeguard. Emergency response times on remote beaches may take longer than in urban environments.
Source: NPS GGNRA / CA State Parks — Beach Safety Practices (nps.gov/goga); SF Fire Dept / NPS Joint Coastal Safety Advisory (sf-fire.org)
Before You Go Near the Water
01
Read the swell period before you approach the water. The number in the chart above is your warning. A period of 15+ seconds means sets are arriving with long, quiet intervals between them — sometimes up to 20 minutes of calm. During the quiet periods between sets, energy is building offshore. People who walk to the water's edge during the lull are swept in when a set arrives.
02
Watch the ocean. Stay on dry sand. Do not approach wet sand or the water's edge until you have watched the ocean and learned the rhythm of the sets.
03
Wet rocks or sand mark where the ocean has already been. If the rocks or sand are wet, a wave reached them recently. Stay above the wet line — always.
04
A long wait between waves is a warning. During long period swells, stay vigilant. The ocean may appear completely calm between sets. Do not be fooled. If it has been calm for several minutes, stay back. Do not walk toward the water.
05
Keep dogs on leash. Keep dogs on leash and away from the water's edge.
06
Tell someone your plans. Leave your destination and expected return time with someone before you go.
How to Read Sets
Long-period swell doesn't produce a steady stream of waves. It travels in sets — groups of larger waves separated by long, quiet intervals. At 15+ seconds, those intervals can stretch to 20 minutes of calm. During the quiet periods between sets, energy is building offshore. People who walk to the water's edge during the lull are swept in when a set arrives.
1
Find a high vantage point above the water line. Do not approach the shore first. Watch from above.
2
Time the quiet intervals. Count the seconds — or minutes — between large waves. This is your set interval.
3
Watch for at least 15 minutes. You need to see multiple sets before you understand the rhythm. One quiet stretch means nothing.
4
The largest wave in a set is not always the first. Sets build in size. The final wave is frequently the biggest.
5
When in doubt, stay back. At 15+ seconds period, stay completely clear of the shore and any rocks.
6
Long-period swells create “sneaker waves,” sometimes called “sleeper waves,” because they produce sets of waves separated by long periods of relative calm. That calm can create a false sense of security — people approach the shore and are not anticipating the next set when it arrives, leaving no time to retreat. These circumstances are predictable and deaths from being swept in are preventable.
Ocean Emergency
911Año Nuevo State Park · (650) 879-2025
CA State Parks Emergency · (800) 952-5580
USCG San Francisco · (415) 399-3547