These three measurements are not the same kind of thing, and treating them as interchangeable would be the easiest way to mislead on this page. One is read off a published federal map, one is a household survey estimate, and one is modeled from weather data. Only the first carries a federal designation at all — and even that designation describes land, not a safety line that any ZIP code has crossed.
Flood exposureFEMA flood mapMapped · not modeled
This is how much of a ZIP code's land sits inside the 1% annual-chance floodplain — the area FEMA maps as the Special Flood Hazard Area, often nicknamed the "100-year floodplain." Despite that nickname it does not mean one flood per century: the 1% chance applies every single year, so such floods can strike in back-to-back years. It is read off FEMA's published flood maps rather than modeled, and it describes land, not any particular home.
FEMA National Flood Hazard Layer — the Special Flood Hazard Area (1% annual chance). A federal flood-map designation of land; it is not a health limit, and no ZIP on this page is described as having crossed a safety line.
Households with no vehicleCensus survey estimateACS · ZCTA-native
This is the share of households in a ZIP code with no vehicle available, from the Census Bureau's American Community Survey. It counts households rather than people, it is an estimate drawn from a sample rather than a full census, and it says nothing about why a household has no car. Next to flood exposure it is a logistical fact and nothing more: an evacuation that assumes a car is harder without one.
US Census Bureau, American Community Survey — a survey estimate carrying sampling error. There is no federal reference level for this measure, and none is implied.
Humid-heat daysModeled heat stressOccupational reference — not federal
This is the average number of days a year when the daily-high wet-bulb globe temperature reaches 28 °C — a heat-stress measure that combines temperature, humidity, sun and wind. Humidity matters because it slows the body's main way of cooling itself, sweat evaporating from the skin, so the same air temperature is harder on the body when the air is humid. The count is modeled across a 2011–2020 climatology, not measured at your address.
Cornell wet-bulb globe temperature data. The 28 °C line comes from NIOSH/ACGIH occupational heat-stress guidance written for workplaces — it is not a federal environmental limit, and reaching it is not a regulatory exceedance.