Storm-prep guide · Updated October 17, 2026

El Niño storm prep for Marin County: a 2026–27 homeowner checklist

A practical, sourced checklist for the 2026–27 El Niño winter in Marin County. Jump to the printable checklist.

Marin's winters already test homes: steep hillsides, creeks that rise fast, older roofs and crawlspaces that stay damp. This guide pulls the most useful preparation steps into one place, with links to the official county and federal sources behind each one. Print the one-page checklist at the bottom, share it with your neighbors, and work through it before the first big storm.

Why this winter matters

As of the NOAA Climate Prediction Center's ENSO Diagnostic Discussion issued October 8, 2026, an El Niño Advisory is in effect. CPC says El Niño "continues to strengthen," with a strong-to-very strong event likely through January–March 2027 (greater than an 83% chance), and the Niño-3.4 index reached +2.1°C last month. CPC also stresses that with an event this strong, the chances of typical El Niño impacts are "larger, though not guaranteed." In other words: a wet winter is more likely, not certain. The next CPC update is scheduled for November 12, 2026.

For Marin homeowners, the practical takeaway is simple: do the cheap, boring prep now (gutters, drains, sandbags, alerts, photos) while contractors and supplies are easy to get, rather than during the first atmospheric river.

Before the storm: roof, gutters and downspouts

• Clear gutters and downspouts of leaves and needles, and check that every downspout empties well away from the foundation, not against it.
• From the ground (binoculars help), look for missing, cracked or lifted shingles, loose flashing around chimneys and vents, and sagging gutters.
• Check the attic on a dry day for daylight through the roof deck, old water stains or damp insulation. These are the spots most likely to leak first.
• Don't climb onto a wet or steep roof. If something looks wrong, get it looked at by a licensed roofer before the rain. You can check any contractor's license with CSLB.

Our roof site has a deeper, roof-only checklist: El Niño roof prep for Marin homes.

Drainage around your home

• Walk the property during a light rain and note where water pools, especially against the foundation, at the bottom of driveways and along hillside retaining walls.
• Clear yard drains, catch basins and the storm drain in front of your house (only if safe to reach) so runoff has somewhere to go.
• Rake leaves away from drain inlets and keep the curb gutter clear.
• Never connect a roof downspout or yard drain to the sanitary sewer cleanout. Marin sanitary districts prohibit it (see, for example, Sanitary District No. 5's code and San Rafael Sanitation District's guidance), and it can overload the sewer during storms.
• If you're on a hillside, watch for new cracks in soil or pavement, tilting fences or retaining walls, and muddy water where there was none. Ready.gov notes that floods can also trigger landslides.

Sump pumps and crawlspaces

Marin County Public Works advises people in flood-prone areas to test their sump pumps and stock up on sandbags ahead of high tides and storms.

• Pour a bucket of water into the sump pit and confirm the pump turns on, empties the pit and shuts off.
• Check that the discharge line is attached and drains away from the house.
• Consider a battery backup if your pump is critical, since storms and outages often arrive together.
• Look into the crawlspace with a flashlight: standing water, wet insulation or a musty smell now means a bigger problem later.

Sandbags: where Marin residents get them

The Marin County Office of Emergency Management recommends buying sandbags from a local hardware store before a storm, because free supplies can run out, some sites limit bags per household, and you should bring your own shovel. The county keeps an up-to-date list of free emergency sandbag locations across Marin (the page was last updated October 14, 2026), including sites in San Rafael, Novato, Mill Valley, Larkspur, Kentfield, Corte Madera, Ross, Fairfax, San Anselmo, Sausalito, Tiburon, Belvedere and West Marin. Some towns post their own details too, such as Novato and Larkspur.

Use the county's sandbag list for the current locations near you, since sites can change during the season.

Trees and outdoor items

• Look for dead limbs over the roof, driveway or power lines, and leaning trees on saturated slopes. Have an arborist assess anything large.
• Never trim near power lines yourself.
• Tie down or store patio furniture, umbrellas, trash bins and anything that could become a projectile or block a drain.

Sewer laterals and backflow

Your sewer lateral is the private pipe between your house and the public sewer main, and in most of Marin the property owner is responsible for it. In wet weather, rainwater gets into cracked laterals and can overload the system. A backwater prevention device (backwater valve) helps stop sewage from flowing back into your home if there's a blockage.

• Find your sewer cleanout and check that its cap is in place.
• Keep wipes, grease and oils out of drains, especially before storms.
• Ask a licensed plumber whether your home has a working backwater device. Requirements vary by district. Sanitary District No. 5, for example, requires a backflow device on new connection permits.

Flood zone lookup and flood insurance

• Look up your address on FEMA's Flood Map Service Center, or use MarinMap's FEMA Flood Info tool, which also lists each Marin town's floodplain administrator.
• Ross Valley homeowners can see the county's Flood Control Zone 9 (Ross Valley) map.
• Ready.gov points out that standard homeowner's insurance does not cover flooding, and that a flood policy typically takes up to 30 days to take effect. If you want coverage, don't wait for the forecast.

Documents and insurance photos

• Walk through every room and take a slow video of your home, contents, appliances and serial numbers. Include the outside, roof (from the ground) and crawlspace.
• Save copies of your insurance policy, the claims phone number and photo IDs in cloud storage and in a waterproof bag.
• Know where your water shutoff, gas shutoff and electrical panel are, and make sure everyone in the house does too.

Alerts: sign up now

• AlertMarin is the county's primary emergency notification system for flooding, evacuations and other emergencies, sent by call, text or email to the addresses you register. Sign up for AlertMarin here. The county also suggests saving the AlertMarin number, 877-627-1411, as a contact and allowing it through Do Not Disturb.
• Nixle provides additional local information. Per the county's alerts page, text your ZIP code to 888-777 to sign up.
• For forecasts, flood watches and warnings, follow the National Weather Service Bay Area office.

Your go-kit

Ready.gov's basic kit list includes water (one gallon per person per day for several days), at least a several-day supply of non-perishable food, a flashlight, a battery or hand-crank radio, a first aid kit, extra batteries, medications and phone chargers. Add copies of important documents, cash, pet supplies, and sturdy shoes. ReadyMarin.org has Marin-specific preparedness checklists and classes.

During the storm

• Follow official instructions. If an evacuation order comes through AlertMarin, leave.
• Do not walk, swim or drive through floodwater. Ready.gov warns that just six inches of moving water can knock you down. Turn around, don't drown.
• Don't touch electrical equipment if it's wet or you're standing in water.
• Use a generator only outdoors and away from windows.
• If there's an immediate threat to life or property, call 911. For non-emergency storm issues in unincorporated Marin, County Public Works lists 415-473-6530 during business hours.

The first hour after water gets in

1. Safety first. If water is near outlets, appliances or the panel, don't wade in. Turn off power at the panel only if you can reach it while standing somewhere dry. Ready.gov advises turning off electricity to prevent shock only if it's safe to do so.
2. Stop the source if you can: shut the main water valve for a plumbing leak, or redirect runoff with sandbags.
3. Photograph everything before you move or throw anything away.
4. Call your insurer to open a claim and ask what they need from you.
5. Start removing water and move valuables, rugs and furniture to dry areas.
6. Call a water damage pro if water reached walls, flooring or the crawlspace.

Our water damage site covers this in much more depth: Marin El Niño flood prevention and the first hours after water gets in.

Mold prevention in the first 24–48 hours

The EPA says it is important to dry water-damaged areas and items within 24–48 hours to prevent mold growth. That clock is why fast action matters.

• Open windows when it's dry outside, run fans and a dehumidifier, and pull up wet rugs.
• Remove soaked items that can't be dried quickly.
• EPA also advises not to run your HVAC system if you know or suspect it's contaminated with mold.

For a day-by-day drying plan, see After the storm: drying and mold-prevention timeline.

Roof leak triage

• Put a bucket under the drip and move belongings out of the way.
• If a ceiling is bulging with water, keep people out from under it and call a pro. Don't stand under a sagging ceiling.
• Note where and when it leaks (wind direction, heavy rain only, constant drip). This helps a roofer find the source.
• Don't go on the roof during a storm. Emergency tarping is a job for a licensed roofer.

When to call a pro

• Water has reached drywall, flooring, insulation or the crawlspace
• Sewage or floodwater is involved
• A ceiling is sagging or a roof leak keeps coming back
• You smell mustiness or see mold days after a leak
• Storm damage to the roof, trees or drainage that you can't safely inspect

Always verify a contractor's license on CSLB's license check before you hire, and be cautious of anyone going door to door after storms.

Sources

• NOAA Climate Prediction Center, ENSO Diagnostic Discussion, Oct 8, 2026
• Marin County Office of Emergency Management, Emergency sandbags
• Marin County Office of Emergency Management, Sign up for AlertMarin and Get Critical Alerts
• Marin County Public Works, Prepare for winter storms
• City of Novato, Where to get sandbags; City of Larkspur, Sandbags
• FEMA, Flood Map Service Center; MarinMap, FEMA Flood Info; Marin County Flood Control District, Zone 9: Ross Valley map
• Ready.gov, Floods and Build a Kit; ReadyMarin
• U.S. EPA, A Brief Guide to Mold, Moisture and Your Home
• San Rafael Sanitation District, Sewer Laterals; Sanitary District No. 5 of Marin County, Sanitary Code
• National Weather Service, San Francisco Bay Area office
• Contractors State License Board, Check a License

Frequently asked questions

Print the checklist Call (628) 336-1777

This guide is general information, not legal, insurance or medical advice. Sources are linked in the text. North Bay Pros is a referral service and doesn't perform the work.