Thornton State Beach

Daly City, California
Managed by The Swim Guide

Photo by Phil King

*This beach is closed to the general public at this time due to damage and continuous danger from landslides, however locals still access this site for hiking, horseback riding, and beach activities. There are some multi-purpose trails, some covered with vegetation or sandy dunes, that wind down closer to the ocean, but these trails have not been maintained and may be badly eroded.

Thornton State Beach is a 58 acre park located on the Pacific coast of Daly City in the San Francisco Bay Area. It was established in 1955. It is a nice spot to have lunch, enjoy the hiking trails and take in the ocean views. There's only a few parking spots and the locals like it that way so it doesn't get overcrowded. Climate tends to be windy and cold throughout much of the park, so dressing in layers is recommended. During the summer months, fog is common along the coastline. The path can be beaten so hiking boots or comfortable shoes are also appropriate. To access the beach, turn west at the intersection of Skyline Boulevard and John Daly Boulevard and proceed to the dunes on Thornton Beach Road. The Bay Area Ridge Trail begins where the road meets the dunes. The area is dog-friendly but you must keep him leashed to protect the indigenous wildlife around.

COVID-19

Keep your distance from other people.

Practicing social distancing is essential right now. Follow the advice of the health experts. If your community has asked that you remain indoors and away from others, do so. Heading to the beach should only be considered an option if social distancing practices can be followed. Spending a day in any crowded place is the worst thing we can do for our most vulnerable right now and will counter the efforts to curb the virus’ spread.

For more information, please visit the World Health Organization public resource on COVID-19.

Water Quality
  • No data available

  • Current Status
  • This status is based on the latest sample. The Swim Guide updates the status of this beach as soon as test results become available.
For water quality icon legend, click:  
Monitoring Frequency

Thornton State Beach is not sampled

Source Information

San Mateo County conducts weekly sampling at over 43 ocean and fresh water sites throughout the year. Samples are collected on Mondays and analyzed by the San Mateo County Public Health Laboratory for the levels of three indicator bacteria. Results are posted to their website within 48 hours. Swim Guide checks for the latest results daily.

The standards for indicator bacteria are as follows:
Single sample maximum
Total Coliform > 10,000 MPN (Most Probable Number) / 100 ml of water
Enterococcus > 104 MPN / 100 ml
E.coli > 400 MPN / 100 ml

Geometric Mean (5 samples collected over a 30 day period)
Total Coliform > 1,000 MPN / 100 ml of water
Enterococcus > 35 MPN / 100 ml
E.coli > 200 MPN / 100 ml

A beach is marked Green when bacteria levels for a single day and geometric mean are below the standards mentioned.

A beach is marked Red when bacteria levels for a single day or the geometric mean are above the standards mentioned.

A beach is marked Grey when there is no current or reliable monitoring information available.

Please contact Greg Smith of County Environmental Health by email GJSmith@smcgov.org or phone (650) 372-6200 if you are interested in becoming a volunteer to help collect water samples at your favorite beach.

If you think you’ve contracted an water related illness please send us a pollution report, see your doctor and contact County Environmental Health Services at (650) 372-6200 to make a report. They will need your name, the dates and areas you were swimming, symptoms and contact information for your or your health care provider.

Water Quality Graph

Thornton State Beach

Daly City, California
Managed by The Swim Guide

COVID-19

Keep your distance from other people.

Practicing social distancing is essential right now. Follow the advice of the health experts. If your community has asked that you remain indoors and away from others, do so. Heading to the beach should only be considered an option if social distancing practices can be followed. Spending a day in any crowded place is the worst thing we can do for our most vulnerable right now and will counter the efforts to curb the virus’ spread.

For more information, please visit the World Health Organization public resource on COVID-19.

Water Quality
  • No data available
  • Current Status
  • This status is based on the latest sample. The Swim Guide updates the status of this beach as soon as test results become available.
For water quality icon legend, click:  

Photo by Phil King

*This beach is closed to the general public at this time due to damage and continuous danger from landslides, however locals still access this site for hiking, horseback riding, and beach activities. There are some multi-purpose trails, some covered with vegetation or sandy dunes, that wind down closer to the ocean, but these trails have not been maintained and may be badly eroded.

Thornton State Beach is a 58 acre park located on the Pacific coast of Daly City in the San Francisco Bay Area. It was established in 1955. It is a nice spot to have lunch, enjoy the hiking trails and take in the ocean views. There's only a few parking spots and the locals like it that way so it doesn't get overcrowded. Climate tends to be windy and cold throughout much of the park, so dressing in layers is recommended. During the summer months, fog is common along the coastline. The path can be beaten so hiking boots or comfortable shoes are also appropriate. To access the beach, turn west at the intersection of Skyline Boulevard and John Daly Boulevard and proceed to the dunes on Thornton Beach Road. The Bay Area Ridge Trail begins where the road meets the dunes. The area is dog-friendly but you must keep him leashed to protect the indigenous wildlife around.

Monitoring Frequency

Thornton State Beach is not sampled

Source Information

San Mateo County conducts weekly sampling at over 43 ocean and fresh water sites throughout the year. Samples are collected on Mondays and analyzed by the San Mateo County Public Health Laboratory for the levels of three indicator bacteria. Results are posted to their website within 48 hours. Swim Guide checks for the latest results daily.

The standards for indicator bacteria are as follows:
Single sample maximum
Total Coliform > 10,000 MPN (Most Probable Number) / 100 ml of water
Enterococcus > 104 MPN / 100 ml
E.coli > 400 MPN / 100 ml

Geometric Mean (5 samples collected over a 30 day period)
Total Coliform > 1,000 MPN / 100 ml of water
Enterococcus > 35 MPN / 100 ml
E.coli > 200 MPN / 100 ml

A beach is marked Green when bacteria levels for a single day and geometric mean are below the standards mentioned.

A beach is marked Red when bacteria levels for a single day or the geometric mean are above the standards mentioned.

A beach is marked Grey when there is no current or reliable monitoring information available.

Please contact Greg Smith of County Environmental Health by email GJSmith@smcgov.org or phone (650) 372-6200 if you are interested in becoming a volunteer to help collect water samples at your favorite beach.

If you think you’ve contracted an water related illness please send us a pollution report, see your doctor and contact County Environmental Health Services at (650) 372-6200 to make a report. They will need your name, the dates and areas you were swimming, symptoms and contact information for your or your health care provider.

Water Quality Graph

  Beach Location Water Quality
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San Francisco, California
San Francisco, California
San Francisco, California
Swim Guide
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Swim Guide shares the best information we have at the moment you ask for it. Always obey signs at the beach or advisories from official government agencies. Stay alert and check for other swimming hazards such as dangerous currents and tides. Please report your pollution concerns so Affiliates can help keep other beach-goers safe.

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