Hardiness zone finder

This lookup runs in your browser, so it needs JavaScript. It reads the 2023 USDA Plant Hardiness Zone Map, produced for the USDA Agricultural Research Service by the PRISM Climate Group at Oregon State University, and reports the half zone recorded for a US ZIP code together with the average annual extreme minimum temperature band that defines it. With JavaScript off you can look the same ZIP up on the USDA's own zone map, which is the source this page reads. The explanation below of what a zone does and does not tell you is worth reading either way.

How this works

A USDA hardiness zone is one number: the average annual extreme minimum temperature at a place, taken over thirty years and rounded into ten-degree Fahrenheit bands. Zone 7 covers places whose coldest night of the year averages between 0 and 10 °F. Each zone is split into an "a" half and a "b" half five degrees apart, so zone 7a averages 0 to 5 °F and zone 7b averages 5 to 10 °F. The 2023 map this tool reads was produced by the PRISM Climate Group at Oregon State University for the USDA Agricultural Research Service, from weather station records for 1991 to 2020, interpolated onto a grid fine enough to show a valley as colder than the ridge above it. Three things follow from that definition, and all three matter more than the number itself. The first is that a zone is an average, not a floor. Your zone says what a cold night usually looks like where you live, not what the coldest night on record was; a plant rated for your zone can still be killed by a winter that runs several degrees below normal. The second is that a zone says nothing about heat, humidity, rainfall, soil or the length of the growing season. A plant hardy in zone 9 in coastal Oregon may not survive a zone 9 summer in central Texas, because the winter low is the only thing the two places share. The third is that zones moved when the map was revised: about half of the United States shifted half a zone warmer between the 2012 map and the 2023 one, partly because the climate warmed and partly because the newer map used better interpolation and a different thirty-year window. A plant tag printed before 2023 may name a zone from the older map. This lookup covers United States ZIP codes only. It has nothing to say about Canada, which uses its own hardiness system, or about anywhere else. Where a ZIP spans a zone boundary, the value shown is the one the zone data records for that ZIP as a whole, and your own garden may sit on the warmer or the colder side of the line. Slopes, walls, paving, water and shelter all move a planting site by a half zone or more in either direction, which is why an experienced gardener treats the zone as the starting question rather than the answer.

Using the result

Use the zone as a filter, not a promise. When a plant is listed as hardy in zones 5 to 9 and you are in zone 6b, winter cold is unlikely to be what kills it, and you can move on to the questions that will: light, drainage, summer heat and water. When your zone sits outside a plant's range by a half zone, gardeners often still grow it, in a sheltered spot, with mulch over the roots, or in a pot that spends winter indoors — that is a deliberate gamble rather than a mistake. When it sits outside by two zones or more, the plant is an annual where you live, whatever the tag says. Zone numbers appear on every plant page on this site, with the source that states them. They are worth reading alongside the frost dates for your ZIP, which answer a different question: not how cold the winter gets, but how long the growing season between frosts is. The two together are most of what a catalogue description assumes you already know.