Key Takeaways
- Wait 72 hours after rain near urban areas. Storm drains flush bacteria and chemicals. Risk increases near river mouths and storm drain outfalls.
- Storm drains near surf breaks spike bacteria 10-100x after rain. Highest risk: near river mouths and in enclosed bays. Open coast clears faster.
- Check Heal the Bay or Surfrider water quality reports. Choose open-coast breaks far from drains. Shower immediately after surfing post-rain.
The Short Answer
The standard recommendation from the Surfrider Foundation and public health agencies is wait 72 hours after rain before surfing near urban areas. Storm drains flush bacteria (fecal coliform, Enterococcus), chemicals, oil, pesticides, and debris into the ocean. A Surfrider study found 12 extra illness cases per 1,000 surfers exposed to wet-weather runoff. Risk varies by location, rainfall intensity, and proximity to storm drain outfalls and river mouths.
What's Actually in the Water After Rain
Urban runoff carries fecal indicator bacteria (from pet waste, sewage overflows, and homeless encampments), heavy metals (from road surfaces), pesticides and herbicides (from lawns and agriculture), and oil and grease (from parking lots). The EPA's BEACH Act requires monitoring at popular swimming beaches, but surf breaks often fall outside monitored zones.
Risk factors: proximity to a storm drain outfall or river mouth (highest risk — bacteria counts spike 10-100x), rainfall intensity (heavy rain overwhelms treatment systems), and water circulation (enclosed bays flush slower than exposed coastline). Open-coast point breaks far from rivers clear faster than enclosed beach breaks near harbors. The San Diego River mouth, Malibu Creek, and Tijuana River are notoriously polluted after rain.
Storm drains near surf breaks spike bacteria 10-100x after rain. Highest risk: near river mouths and in enclosed bays. Open coast clears faster.
What This Means for Your Session
After rain, avoid breaks near storm drains, river mouths, and harbors for 72 hours. Check local water quality reports — Heal the Bay (California) and Surfrider publish near-real-time beach grades. If you must surf sooner, choose an open-coast break far from runoff sources with good water circulation. Avoid getting water in your mouth, eyes, and open cuts. Shower immediately after. Ear plugs reduce ear infection risk. If you develop fever, gastrointestinal symptoms, or ear/sinus infection within 72 hours of surfing post-rain, see a doctor and mention ocean exposure.
