What USDA zone am I in — and what climate zone is my house?

Two maps, two jobs

The USDA zone on a shrub tag does not tell you how much attic insulation the IECC expects. The IECC zone on a building permit does not tell you whether bermudagrass will survive your winter.

USDA Plant Hardiness Zone

The USDA map is based on average annual extreme minimum temperature — the coldest night a location typically sees, averaged over years. Zone numbers run from coldest (lower numbers) to warmest. Subzones a and b split each 10°F band in half.

For lawn work, the zone sets expectations for which grasses are perennial, which need overseeding every year, and which warm-season species are realistic. Pair it with grass identification — the zone tells you what can live; the species tells you what you actually have.

DOE / IECC climate zone (your house)

DOE's Building America program publishes climate zones aligned with the International Energy Conservation Code (IECC). Pacific Northwest National Laboratory's Guide to Determining Climate Zone by County (PNNL-33270, 2022) assigns each U.S. county to a zone number (1–8) plus a moisture regime (A humid, B dry, C marine).

You need this for insulation levels, window ratings, and HVAC discussions — not for choosing grass seed. If you are sizing a furnace or arguing about R-value, use the county table, not the USDA map.

Our twelve regions (USDA range + timing)

Upkeep Plan groups the lower 48 into twelve maintenance regions. Each carries a USDA hardiness range and a turf season type. For when to overseed, apply pre-emergent, or winterize sprinklers, use the soil-temperature reading — not the zone alone.

Pick your state, open the matching region, and check today's soil temperature — that is the number that moves every day.

Questions people actually ask

What is a USDA Plant Hardiness Zone?

The USDA map divides North America into zones based on the average annual extreme minimum winter temperature. Each zone represents a 10°F band (zone 6 is −10 to 0°F, for example), subdivided into a and b halves. It tells you which perennial plants — including turfgrass — typically survive the winter, not how hot your summers are.

What is a DOE or IECC climate zone?

The U.S. Department of Energy Building America program publishes climate zones for residential energy performance — insulation, windows, HVAC sizing, and code compliance. They are assigned by county and combine temperature regions with moisture regimes (A, B, C). A house in zone 5 and a lawn in USDA zone 6 can both be correct; they measure different things.

How do I find my USDA zone by ZIP code?

Use the USDA Agricultural Research Service interactive map at planthardiness.ars.usda.gov — enter your ZIP code. That is the authoritative source. Our twelve maintenance regions group states into broader bands; pick the region that matches your state on the Is It Time? page for soil-temperature timing.

How do I find my IECC climate zone?

DOE's Guide to Determining Climate Zone by County (Pacific Northwest National Laboratory, PNNL-33270) lists the IECC and Building America designation for every U.S. county. The data files and map are on the Building America Solution Center at basc.pnnl.gov.

Why does this site use regions instead of my exact zone?

Lawn timing follows soil temperature measured daily, not a static zone label. The twelve regions match how turf behaves — cool-season, warm-season, or transition — and carry a USDA range for context. Your exact half-zone still matters for plant shopping; your region slug matters for when to overseed or blow out sprinklers.

Sources

• USDA Agricultural Research Service — Plant Hardiness Zone Map: official ZIP lookup and zone definitions.
• Pacific Northwest National Laboratory — Guide to Determining Climate Zone by County: Building America and IECC 2021 Updates (PNNL-33270): county-level DOE/IECC zones.
• Building America Solution Center — climate zone data files: GIS and county tables.