El Niño 2026-2027 Flooding and Storms
Get prepared NOW!
In Southern Marin, El Niño winter storms can bring:
- Heavy and prolonged rainfall
- Creek, roadway, and low-lying-area flooding
- Coastal and bayside flooding
- Landslides, mudslides, and debris flows
- Downed trees and power lines
- Power outages
- High surf and coastal erosion
- Road closures and transportation disruptions
How to stay informed during winter storms?
- Sign up for alerts and warnings.
- Bookmark the Marin County El Niño Portal.
- Bookmark the Marin Office of Emergency Management – Public Emergency Portal (see map below).
- We will also post regular updates to this City of Mill Valley website.

The City of Mill Valley strongly encourages businesses and residents to prepare for the upcoming rain and potential flooding.
- Sign up for AlertMarin, the County’s primary emergency alerting system for flooding and fire.
- Sign up for Nixle, Mill Valley Police Department will share local road closures and hazards. Just text your zip code to 888-777.
- Bookmark the Marin County El Niño Portal.
- Bookmark the Marin Office of Emergency Management – Public Emergency Portal.
- Review family emergency plans.
- Assemble or refresh emergency supply kits.
- Prepare your home by clearing gutters, drains, filling sandbags, servicing pumps, etc.
- Secure yard and garden furniture, trash cans, trampolines and any items that might blow away and cause damage during a storm.
- Prepare Construction Sites and Schedule Work Accordingly. Maintain erosion control measures at construction sites, including the minimum erosion control measures (pdf) and best practices to reduce water pollution(pdf). Keep the weather in mind when scheduling work and respect the city’s moratorium on grading during the winter months of October through April (link).
Alerts
In Southern Marin, El Niño winter storms can bring:
- Heavy and prolonged rainfall
- Creek, roadway, and low-lying-area flooding
- Coastal and bayside flooding
- Landslides, mudslides, and debris flows
- Downed trees and power lines
- Power outages
- High surf and coastal erosion
- Road closures and transportation disruptions
Special Advisory to Residents in Low-Lying Areas
Mill Valley has had a history of experiencing localized flooding in low-lying areas. If you live in an area that has a history of flooding, it is highly recommended that you be proactive now and stay alert.
- Monitor the local creek and tide levels.
- Consider moving personal belongings to higher ground, including vehicles.
- “Turn around, don’t drown”: never drive through standing or moving water. Even shallow water can carry a car away or leave you stranded in your vehicle.
- Avoid walking in flood waters and keep out of creeks and waterways during the storm.
- Avoid down power lines.
- If conditions worsen, the Police and Fire Departments recommend you shelter in place.
- Make sure you are signed up for AlertMarin and Nixle.
- Secure garbage cans, lawn furniture, trampolines and anything that could become airborne and cause damage.
- Clean out gutters, storm drains, etc. (keeping drains clear of trash, leaves and branches).
- Fill sandbags if you live in areas prone to run off and flooding.
- Monitor king tides and forecasts.
- Keep out of creeks and waterways during the storm.
- Maintain erosion control measures at construction sites and respect the City’s moratorium on grading during the winter months.
Flooding or fallen trees may cause traffic back-ups and road closures. Road closures will be posted on our homepage at www.cityofmillvalley.gov and through Nixle alerts.
Drive with caution:
- When driving in the rain, use extra caution and always have your headlights on. Remember, if you turn on your windshield wipers, turn on your headlights.
- Please obey the speed limits and follow other traffic at a safe distance.
- If traffic signals are out or flashing red, come to a full stop at every intersection, and proceed as you would at a four-way stop.
- Never drive through standing or moving water. Even shallow water can carry a car away or leave you stranded in your vehicle.
Residents are advised of possible downed trees and power lines. Report downed power lines by calling 911 and PG&E at 1-800-743-5002. Stay away from the downed powerlines and always assume they are energized and dangerous.
- Check the PG&E Outage Map for updates.
- Stay well away from downed powerlines
- Make sure you have batteries for flashlights and fully charged back-up battery packs for your devices.
- Keep freezers and refrigerators closed.
- Use gas and propane generators outdoors and 20ft from your home.
- Do not use a gas stove to heat your home.
- Disconnect electronics to avoid damage from electrical surges.
- If safe, go to an alternate location for heat and power if needed.
- Check on your vulnerable neighbors.
If you see a downed power line call 911 immediately. For more safety information about downed power lines visit PG&E’s website.