Photo: David M. Green · CC BY-SA 3.0Storms, floods and disasters in Onset
Onset isn’t graded for hazard risk: Onset is a Census area inside a town, graded with the town.
What Onset faces
Each hazard’s share of the building damage FEMA expects here, and how its rate compares with the rest of the country.
River and rain flooding
Coastal flooding
Hurricanes
Shares are of FEMA’s expected building damage, the measure the grade uses; ranks compare each hazard’s building-damage rate with all 85,154 U.S. census tracts. In FEMA’s terms, river and rain flooding is FEMA’s “Inland Flooding” (rivers and streams overflowing their banks, or rain overwhelming drainage). FEMA defines coastal flooding as high or rising tides and storm surge, so surge damage is counted there. Drought isn’t listed: FEMA counts its losses in crops only.
Does Onset flood? No paid flood claims on record
FEMA’s records show no paid flood insurance claims in Onset. That’s not a promise: most homes don’t carry flood insurance, so small floods go unrecorded.
Onset isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.
Insurance rates: Plymouth County.The storms Onset remembers
None of the 25 disasters declared for Plymouth County shows FEMA aid or repair money reaching Onset itself in FEMA’s records, so these are its biggest flood-claim years.
Plymouth County has had 25 natural disasters declared by the President since 1953, most often hurricanes and tropical storms, then severe storms. Not counted: the 2005 Hurricane Katrina evacuee emergency, which covered counties that took in evacuees.
Get ready for what Onset faces
A short kit for the hazards that drive the building damage here, what to check before you buy, and where neighbors get alerts.
- Turn around at flooded roads: a foot of moving water can carry off a car.
- Flood insurance usually takes 30 days to start, so buy it before the forecast.
- Keep papers and medicines up high, in a grab-and-go bag.
- Know your evacuation zone and the way off the coast.
- Storm surge comes fast: leave when you’re told, not when the water arrives.
- Move cars to high ground before king tides and nor’easters.
- The season runs June through November and peaks from mid-August to mid-October.
- Bring in porch furniture and anything the wind can throw.
- Fill the gas tank and charge phones before the storm arrives.
- Look up the address on FEMA’s flood map.
- Ask the seller or landlord whether it has ever flooded, and what flood insurance costs there.
- Get a flood insurance quote early: policies usually start 30 days after you buy.
Know where neighbors sign up for alerts? Add it to the Handbook so everyone has it.
Questions about natural hazards in Onset
Is Onset in a flood zone?
Flood zones are drawn street by street, so the answer depends on the address: look it up on FEMA’s flood map. In Plymouth County, 52% of homes in mapped flood zones carry federal flood insurance, and 4.3% of all homes do.
How much is flood insurance in Onset?
FEMA’s Community Rating System list shows no discount for Onset’s flood program. Premiums depend on the building; policies usually start 30 days after you buy, so get a quote early.
Storm stories
Memories, warnings and help from neighbors in Onset.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where Onset’s residents lived in the 2020 census; OpenFEMA: NFIP redacted claims, multiple-loss properties, community status book and residential penetration rates, housing assistance (owners and renters), public assistance funded projects, hazard mitigation properties and disaster declarations. Homes: Census ACS 2020–24. Preparedness tips: Ready.gov. FEMA’s model is an average of expected damage, not a forecast. How hazard risk is graded.