Coastal Signal Inc

Coastal Signal is a San Francisco-based company that forecasts beach water quality across California, helping people understand conditions before delayed laboratory results are available. It produces a daily water-quality flag and a five-day outlook for individual beaches, updating forecasts each morning before new test results arrive. The service addresses gaps in conventional monitoring: samples can take a day or more to process, and beaches may be tested weekly or monthly.

Coastal Signal draws on years of county laboratory results, combined with information on rainfall, creek flow, tides, waves, and sewer discharges. Because factors affecting water quality vary by location, it builds beach-specific forecasts. Its map presents forecasts alongside county officials’ status rather than replacing official calls, and indicates when data is too outdated to support a forecast.

Coastal Signal works with surf, weather, and outdoor apps, local media, county health agencies, and researchers to make information accessible to beachgoers. The company is also developing rip-current research using surf cameras and lifeguard records. Its forecasts are informational, not public health advisories.