Half Moon Bay — Sea temperature now
Popular Central California beach near Half Moon Bay.
Very warm water with a light chop and a light breeze — great swimming conditions.
Location
Half Moon Bay on the map, with nearby beaches and live sea temperatures.
7-day forecast
Water, air, waves, wind and UV outlook for the week ahead.
Monthly sea temperature averages
Typical year-round water temperature, based on regional climatology.
Best time to swim in Half Moon Bay
The sea in Half Moon Bay peaks in August, when the water averages around 16°C.
On average, 0 months a year sit above 20°C — the threshold most swimmers describe as pleasant without a wetsuit.
Outside peak season the water drops toward 12°C, so a 3/2mm shorty or full wetsuit makes long swims much more comfortable.
The coldest month is typically January at around 12°C, when cold-water swimmers dominate the coast.
Half Moon Bay sea temperature history
Long-term climatology for Half Moon Bay shows an annual mean sea temperature of 14°C, ranging from 12°C in winter to 16°C at the summer peak.
The seasonal swing is roughly 4°C between the coldest and warmest month — a useful yardstick when comparing years or checking whether the current sea is running above or below average.
Recent decades have trended slightly warmer at Half Moon Bay, in line with regional sea-surface temperature records for the wider basin.
Monthly averages below are drawn from multi-decadal climatology and are updated as new observations arrive.
Half Moon Bay sea temperature: frequently asked questions
What is the warmest month to swim in Half Moon Bay?
August is the warmest month in Half Moon Bay, when the sea averages about 16°C. Late-season warmth often persists a few weeks after peak.
When is the sea coldest in Half Moon Bay?
The coldest month in Half Moon Bay is typically January, when the water averages around 12°C. Cold-water swimmers and surfers dominate this period.
When can you swim in Half Moon Bay without a wetsuit?
The sea in Half Moon Bay rarely climbs above 20°C, so a wetsuit is recommended year-round for anything longer than a quick dip.
Do I need a wetsuit in Half Moon Bay?
Outside peak summer the water in Half Moon Bay drops toward 12°C, so a 3/2mm shorty or full wetsuit makes long swims much more comfortable. In peak months most swimmers go without.
What is the average sea temperature in Half Moon Bay?
The long-term annual mean sea temperature in Half Moon Bay is about 14°C, based on multi-decadal climatology of the surrounding waters.
How do I check the current sea temperature in Half Moon Bay?
The live reading at the top of this page shows the current sea temperature in Half Moon Bay, updated hourly from marine buoy and satellite data. The 7-day forecast covers water, air, waves, wind and UV for the week ahead.
Year-round sea temperature
| Month | Sea | Comfort |
|---|---|---|
| Jan | 12°C | Cold |
| Feb | 12°C | Cold |
| Mar | 12°C | Cold |
| Apr | 12°C | Cold |
| May | 13°C | Cold |
| Jun | 14°C | Bracing |
| Jul | 15°C | Bracing |
| Aug ⭐ | 16°C | Bracing |
| Sep | 16°C | Bracing |
| Oct | 15°C | Bracing |
| Nov | 14°C | Bracing |
| Dec | 13°C | Cold |