Sonoma County, CA: home risks and climate
FEMA’s National Risk Index rates Sonoma County “Relatively High” for overall risk relative to other US counties, 13th of 58 counties in California by risk score. The hazards rated Relatively High or Very High here are landslide, earthquake, drought, inland flooding and wildfire. These are relative ratings, not probabilities.
Sonoma County, CA
- Look up your FEMA flood zone, and remember that "minimal hazard" zones still flood.
- Raise or move valuables, the furnace and the water heater off a basement floor where you can.
- Test the sump pump and its backup before the wet season.
- Clear dead leaves and needles from gutters, the roof and under decks.
- Keep the first 5 feet around the house free of anything that burns (mulch, firewood, plants).
- Cover vents with 1/8-inch metal mesh to keep embers out.
- Watch for new cracks in foundations, walls and door frames; drought shrinks clay soils.
- Fix running toilets and dripping faucets.
- If you have a well, know its depth and recent yield.
- Strap the water heater to the wall with two straps.
- Secure tall furniture and TVs to studs.
- Know how to shut off gas at the meter, and only do it if you smell gas.
- Watch for new cracks in the ground, tilting trees or fences, and doors that stick.
- Keep gutters and drains directing water away from slopes.
- Know the signs of a debris flow during heavy rain.
- Check your FEMA flood zone at your address; V and coastal A zones carry wave risk.
- Know your evacuation route and zone before a storm is named.
- Keep a flood-insurance policy in force; there is usually a 30-day wait.
- Use surge protection for electronics; ask an electrician about a whole-home surge protector.
- Keep trees near the house healthy and trimmed.
- Unplug sensitive electronics before a storm if you can.
- Service the AC before the hot season and clear the outdoor unit of debris.
- Change the AC filter; a clogged filter cuts cooling.
- Plan a cool place to go if the power or AC fails.
- Know if you are in a lahar or ashfall zone.
- Keep N95 masks and goggles for ash.
- Have a plan to protect the HVAC system from ash.
- Pick the safe room: lowest floor, interior, no windows. Tell everyone in the house.
- Keep shoes, a flashlight and a helmet for each person there.
- Turn on wireless emergency alerts on every phone.
- Trim dead or overhanging branches before storm season.
- Check that gutters, siding and roof edges are fastened tight.
- Tie down or store outdoor furniture, grills and trampolines.
- Photograph the roof and siding now, so you have a dated before picture.
- Ask about impact-rated (UL 2218 Class 4) shingles when the roof is replaced.
- Know your policy’s wind and hail deductible in dollars.
- Clean gutters so melting snow drains instead of forming ice dams.
- Check attic insulation and air sealing; warm attics cause ice dams.
- Keep a snow shovel, ice melt and a backup heat plan.
- Find out whether your home is in a tsunami hazard zone.
- Know the walking route to high ground.
- Strong shaking near the coast means move to high ground now.
- Know whether your home or access road crosses avalanche paths.
- Follow local avalanche center forecasts in winter.
- Keep supplies for being snowed in for several days.
Winterize outdoor faucets before ~Nov 20. Typical first 32°F night (50% date) at Santa Rosa Sonoma Co Airport, 10 km away. Last freeze ~Mar 2.
Radon Zone 3: lowest predicted indoor radon. EPA recommends testing every home, whatever the zone.
- This weekBefore the first freeze (~Nov 20): disconnect hoses and drain outdoor faucets.
- This weekBefore the first freeze (~Nov 20): shut off and drain or blow out the sprinkler system.
- This monthPress the test button on every smoke and CO alarm.
- This monthCheck the date on the back of every smoke and CO alarm.
- This monthLook under every sink and around toilets and the water heater for drips.
- This monthClean gutters and downspouts after the leaves are down.
What the records say
Plain-language summary of the numbers below, compared with California and the US.
By FEMA’s hazard scores (0 to 100, the share of US counties scoring lower), landslide scores 99.8, earthquake scores 99.5 and drought scores 99.3 in Sonoma County, and modeled expected annual losses from all hazards come to about $604.7 million a year across 488,330 residents.
There have been 36 federal disaster declarations covering Sonoma County in the OpenFEMA record, above the California county median of 24 and above the national county median of 20; 18 came in the last ten years. The most recent was severe winter storms, straight-line winds, flooding, landslides, and mudslides (2023-04-03).
Sonoma County is part of the Santa Rosa-Petaluma, CA metropolitan area.
Flood-insurance (NFIP) records list 7,403 claims in Sonoma County, above the California county median of 300, 974 of them in the last ten years. Of claims with a recorded zone, 12% were outside the mapped high-risk flood zone.
Sonoma County sits in climate zone 3C (warm-marine) in the marine Building America region and EPA radon zone 3.
At Santa Rosa Sonoma Co Airport (10 km from the county’s center), the typical first 32°F night is around Nov 20 and the last around Mar 2 (50% dates, 1991–2020), which sets when to winterize outdoor faucets.
All 18 hazards
FEMA National Risk Index December 2025. Ratings and scores are relative to other US counties, not probabilities. Expected annual loss is FEMA’s modeled average across buildings, people and agriculture.
| Hazard | Risk rating | Risk score | Expected annual loss | Recorded events | Prepare |
|---|---|---|---|---|---|
| Landslide | Relatively High | 99.8 | $5.0M | — | Checklist |
| Earthquake | Relatively High | 99.5 | $283.6M | — | Checklist |
| Drought | Relatively High | 99.3 | $14.4M | 1,610 | Checklist |
| Inland flooding | Relatively High | 99.2 | $279.8M | 71 | Checklist |
| Wildfire | Relatively High | 98.2 | $16.8M | — | Checklist |
| Heat wave | Relatively Moderate | 88.8 | $3.0M | 86 | Checklist |
| Coastal flooding | Relatively Moderate | 68.6 | $1.1M | — | Checklist |
| Lightning | Relatively Moderate | 58.7 | $341,477 | 29,069 | Checklist |
| Volcanic activity | Relatively Low | 85.0 | $2,854 | 1 | Checklist |
| Tsunami | Very Low | 26.2 | $243,872 | 73 | Checklist |
| Hail | Very Low | 16.1 | $59,923 | 1 | Checklist |
| Tornado | Very Low | 15.4 | $162,646 | 9 | Checklist |
| Strong wind | Very Low | 13.6 | $118,873 | 1 | Checklist |
| Avalanche | Very Low | 10.8 | $10 | 0 | Checklist |
| Winter weather | Very Low | 8.1 | $6,414 | 13 | Checklist |
| Cold wave | No Rating | 0.0 | $0 | 0 | Checklist |
| Hurricane | Not Applicable | — | — | — | Checklist |
| Ice storm | Not Applicable | — | — | — | Checklist |
Federal disaster declarations
Each county-level declaration in OpenFEMA DisasterDeclarationsSummaries v2, counted once per disaster number.
| Declared | Event | Type |
|---|---|---|
| 2023-04-03 | Severe winter storms, straight-line winds, flooding, landslides, and mudslides | DR · Severe Storm |
| 2023-03-10 | Severe winter storms, flooding, landslides, and mudslides | EM · Flood |
| 2023-01-14 | Severe winter storms, flooding, landslides, and mudslides | DR · Flood |
| 2023-01-09 | Severe winter storms, flooding, and mudslides | EM · Flood |
| 2020-10-16 | Wildfires | DR · Fire |
| 2020-09-27 | Glass fire | FM · Fire |
| 2020-08-22 | Wildfires | DR · Fire |
| 2020-08-18 | Lnu lightning fire complex | FM · Fire |
| 2020-03-22 | COVID-19 pandemic | DR · Biological |
| 2020-03-13 | COVID-19 | EM · Biological |
| 2019-10-24 | Kincade fire | FM · Fire |
| 2019-05-17 | Severe winter storms, flooding, landslides, and mudslides | DR · Severe Storm |
Showing the 12 most recent of 36.
Flood-insurance claims (NFIP)
Claims filed under the National Flood Insurance Program, from FEMA’s NfipClaims v3 dataset (all years on file), by year of loss.
Inside vs outside the mapped high-risk zone
By the rated flood zone recorded on each claim. Claims outside the high-risk zone are a reminder that “minimal hazard” is not “no hazard”. Check your own zone with an address in the Snapshot.
Climate, radon and freeze
This month’s plan for Sonoma County
Region tasks plus this county’s hazard ratings and freeze dates. Add your ZIP and systems on the Home Plan page to subscribe in your calendar.
November7 tasks
- This weekBefore the first freeze (~Nov 20): disconnect hoses and drain outdoor faucets.
Water left in a hose bib can freeze, split the pipe inside the wall, and only leak when you turn it on in spring.
How
Remove hoses, close the indoor shutoff valve for each outdoor faucet if you have one, and open the outside faucet to drain it.
- This weekBefore the first freeze (~Nov 20): shut off and drain or blow out the sprinkler system.
Frozen water cracks backflow preventers and valves, an expensive spring surprise. (Skip if you have no in-ground irrigation.)
How
Close the irrigation shutoff, then drain per the system’s design or book a compressed-air blowout.
- This monthPress the test button on every smoke and CO alarm.
An alarm you have not heard in months may have a dead battery or sensor. NFPA recommends testing smoke alarms at least once a month.
How
Hold the test button until it sounds. Anything silent or chirping: replace the battery, or the whole alarm if it is past its date.
- This monthCheck the date on the back of every smoke and CO alarm.
Smoke alarms wear out: NFPA advises replacing them 10 years after the manufacture date. CO alarms have their own end-of-life date printed on them.
How
Twist each alarm off its base and read the date. Replace any past its life; swap batteries in alarms that take them.
- This monthLook under every sink and around toilets and the water heater for drips.
Slow leaks rot cabinets and subfloors long before they show. Catching one early is a washer, not a floor.
How
Use a flashlight: feel supply lines and the shutoff valves, look for stains, warped cabinet floors or a toilet that rocks.
- This monthClean gutters and downspouts after the leaves are down.
Blocked gutters overflow at the foundation, rot fascia and, in cold climates, help ice dams form.
How
From a stable ladder (with a helper), scoop debris, then flush each downspout with a hose. Extensions should drop water 4 to 6 feet from the house.
- WatchLook in the attic with a flashlight after the first big storm of the season.
Stains on the roof deck, wet insulation or daylight around vents show leaks early, and droppings show pests.
How
Stay on the joists. Look around chimneys, vent pipes and valleys, the places most leaks start.
December3 tasks
- This monthPress the test button on every smoke and CO alarm.
An alarm you have not heard in months may have a dead battery or sensor. NFPA recommends testing smoke alarms at least once a month.
How
Hold the test button until it sounds. Anything silent or chirping: replace the battery, or the whole alarm if it is past its date.
- WatchDegrease the range-hood filter.
Grease-clogged hood filters stop pulling smoke and grease out of the kitchen and can feed a stovetop fire.
How
Pop the metal filter out and soak it in hot water with dish soap and baking soda, or run it through the dishwasher if the maker allows.
- WatchRun bath and kitchen fans during and after showers and cooking.
In a damp winter, indoor moisture condenses on cold windows and in the attic.
How
Run fans 20 minutes after showers, check the attic for frost or damp sheathing on cold mornings, and wipe window condensation.
Neighbouring counties
Information, not insurance, legal or engineering advice. Ratings describe the county as a whole; your address can differ. Found an error? Send a correction.