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.
- Rain itself is fine; lightning is not. Heavy rain near drains or river mouths starts the runoff clock rather than ending the risk.
- 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.
Surfing While It Is Raining
Rain falling on the lineup is not the hazard. Light rain often thins the crowd and can arrive with calm, glassy conditions, and the water you are surfing in is the same water that was there an hour earlier. The two things that change the answer are what is happening in the sky and what the rain is about to wash into the sea.
Lightning ends the session. If you can hear thunder, you are close enough to be struck, and the ocean offers no cover. Get out, wait until thirty minutes have passed since the last thunder, and only then reassess. Heavy rain is the second signal: it is the start of the runoff problem below, not a separate one. A drizzle at a clean open-coast beach is a normal surf. A downpour next to a storm drain or river mouth is the beginning of the 72-hour clock.
Rain itself is fine; lightning is not. Heavy rain near drains or river mouths starts the runoff clock rather than ending the risk.
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.
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.
Check Heal the Bay or Surfrider water quality reports. Choose open-coast breaks far from drains. Shower immediately after surfing post-rain.
