What Planting Zone Am I In? Find Your USDA Zone by ZIP Code

Your planting zone is your USDA Plant Hardiness Zone: a number (and an “a” or “b” half) that tells you the average coldest night your area sees in a typical winter. Enter your ZIP code below to see your zone from the 2023 USDA map, which was built from 1991–2020 weather data by the PRISM Climate Group at Oregon State University. Then read on, because the number is useful for one specific job — picking perennials, trees and shrubs that survive your winters — and is often misused for things it can’t tell you, like when to plant tomatoes.

What Your Zone Number Means

The USDA Plant Hardiness Zone Map is based on one measurement: the average annual extreme minimum temperature. For every half-mile grid cell in the country, mapmakers took the single coldest temperature recorded each winter, then averaged those yearly lows over 30 years. That average is sorted into 10°F zones running from zone 1 (coldest) to zone 13 (warmest, found only in Hawaii and Puerto Rico).

It is an average of extremes, not the coldest it has ever been. In a zone 6a yard, the coldest night of a typical winter lands around −10°F to −5°F, but a rare cold snap can go lower, and a mild winter may never get close. That is why plants rated right at the edge of your zone can thrive for years and then die in one brutal January.

What the “a” and “b” Mean

Every zone is split into two 5°F halves. The “a” half is the colder one and “b” the warmer one, so 7a sits at 0°F to 5°F and 7b at 5°F to 10°F. Most plant tags and catalogs list whole zones (“hardy in zones 5–9”), so the half zone matters most when you are shopping at the edge of a plant’s range. If you are in 5a and a shrub is rated to zone 5, you are at the coldest end of what it is expected to handle; in 5b you have a 5°F cushion.

A practical rule: when a plant is borderline for your half zone, plant it in the most sheltered spot you have, mulch the root zone before the ground freezes, and treat it as an experiment rather than a centerpiece.

What Your Zone Does Not Tell You

This is where most planting mistakes start. A hardiness zone is a winter-cold number, full stop. The USDA itself notes that wind, soil type, soil moisture, humidity, snow, winter sunshine and summer heat all affect whether a plant survives. Specifically, your zone does not tell you:

• Your frost dates. The average last spring frost and first fall frost are separate climate statistics. Two towns in the same zone can have last frosts several weeks apart because of elevation, distance from water or valley position. Virginia Tech Extension points out that Roanoke County alone contains four hardiness zones, with about a 30-day difference in planting time between them.
• Summer heat. Zone 8 covers humid Gulf Coast towns that bake for months and cool, marine-influenced coastal Pacific Northwest towns where tomatoes struggle to ripen. Many plants fail from heat and humidity, not cold. The American Horticultural Society publishes a separate heat-zone map for that reason.
• Rainfall and humidity. A lavender that is cold-hardy in your zone can still rot in wet, heavy clay over a rainy winter.
• Soil. Hardiness ratings assume reasonable drainage. Poorly drained soil makes plants less winter-hardy, not more.
• Season length. How many frost-free days you get decides whether long-season crops like melons and sweet potatoes finish, and that comes from your frost dates, not your zone.

So for vegetables and annual flowers, look up your average last and first frost dates from your state’s extension service or NOAA climate data and count from those. Our guide to when to plant vegetables walks through that method, and the zone calendars below are written the same way.

The 2023 Map vs. the 2012 Map

The USDA released the current map in November 2023, replacing the 2012 edition. If your zone changed, here is what actually happened:

• Newer data. The 2023 map averages winter lows from 1991–2020; the 2012 map used 1976–2005. That shift alone makes the new map, on average, about a quarter-zone warmer across much of the U.S.
• More stations and better interpolation. The 2023 map draws on 13,625 weather stations, more than the 2012 version, and uses the PRISM model to account for elevation, cold-air drainage, slope and nearby water. Some areas moved to a colder zone because of better data, not cooling.
• Finer detail. Each grid cell is about half a mile on a side, so cities (which hold heat) and hilltops or valleys can show up in different zones than the surrounding countryside.

The USDA is explicit that a changed zone is not a reason to pull out plants that have done well for you, and that zone shifts are not reliable evidence for or against climate change because the map tracks 30-year averages of extreme events. Treat a half-zone change as a small nudge in what you can try, not a rewrite of your garden. Our USDA hardiness zone map guide covers the regional patterns in more detail.

How to Use Your Zone When Buying Plants

Hardiness zones were designed for perennial plants — anything that has to live through winter outdoors. That includes trees, shrubs, perennials, ornamental grasses, fruit trees, berries, spring bulbs and groundcovers. Here is how to read the label and decide.

Read both ends of the range

A tag reading “zones 4–8” means the plant is expected to survive winters down to zone 4 and to perform well up to zone 8. The upper number is about heat, humidity and lack of winter chill — tulips, lilacs, peonies and many apples need a real cold period to flower and fruit well. In zones 9 and 10, the upper number matters as much as the lower one.

Give yourself a cushion for permanent plantings

For a shade tree, hedge or fruit tree you expect to keep for decades, choose plants rated at least one half zone colder than yours, and ideally a full zone. A rare cold snap only has to happen once to kill a 15-year-old tree. Save the zone-pushing for perennials you could replace in a season.

Remember that containers are colder

Roots in a pot above ground are exposed to air temperature on all sides, so they get much colder than roots in the ground. A common rule of thumb is to choose container perennials rated one to two zones colder than yours, or move pots into an unheated garage or against the house for winter.

Check the source of the rating

Zone ratings on tags come from growers’ observations, and they vary. If a rating looks optimistic, cross-check it with your state extension service, a local independent nursery or local Master Gardeners — the USDA recommends exactly that. Our trees and shrubs guide covers site selection and planting once you have picked a hardy plant.

Month-by-Month Planting Calendars by Zone

Once you know your zone, these calendars give a January-to-December plan for vegetables, flowers and bulbs, lawn care and tree and shrub tasks. Every vegetable timing in them is anchored to your own local frost dates (“start peppers indoors 8–10 weeks before your last frost”), because the zone alone can’t tell you when frost ends. Each also links to a zone plant list.

• Zone 5 planting calendar — short season; start warm-season crops indoors and protect fall crops. Plant list: zone 5 plants.
• Zone 6 planting calendar — a moderate season with a strong fall garden window. Plant list: zone 6 plants.
• Zone 7 planting calendar — long season, two good cool-season windows. Plant list: zone 7 plants.
• Zone 8 planting calendar — early spring, hot summers in the South, fall and winter greens. Plant list: zone 8 plants.
• Zone 9 planting calendar — fall and winter are the main vegetable seasons; summer heat is the limit. Plant list: zone 9 plants.
• Zone 10 planting calendar — frost is rare or absent; plan around heat and summer rains. Plant list: zone 10 plants.

How to Find Your Frost Dates

Because zones don’t determine frost dates, look them up separately. Good sources include your state’s land-grant university extension service (most publish planting calendars by region or county), NOAA’s climate normals data, and regional climate centers — Virginia Tech Extension, for example, points gardeners to the Midwestern Regional Climate Center’s freeze date tool for county-level data. Pay attention to whether a date is a 50% probability (half of years will have a frost after it) or a 10% probability; the 50% date is the usual “average,” which means planting tender crops on that exact day is a coin flip. Many extension calendars recommend waiting until one to two weeks after the average date for heat-loving crops like tomatoes, peppers and melons.

Ready to plan the season? Our vegetable gardening hub collects seed-starting, raised-bed and crop guides in one place.

Microclimates: When Your Yard Isn’t Your Zone

The map is drawn at half-mile resolution, which still can’t see your yard. The USDA describes small heat islands from pavement and buildings, and cold pockets where air pools in low spots. In practice:

• A bed against a south- or west-facing brick wall can behave like a half zone warmer.
• The bottom of a slope or a low corner can frost earlier in fall and later in spring than the rest of your property.
• Exposed, windy sites dry out evergreens in winter, causing browning even when temperatures stay within the plant’s rating.
• Reliable snow cover insulates perennials, so a snowy zone 5 garden can be kinder to roots than a bare, windy zone 6 one.

Keep a simple garden journal: which beds frost first, where snow melts first, which plants came through winter. After two or three years you will know your yard better than any map.

Sources

• USDA Agricultural Research Service, 2023 USDA Plant Hardiness Zone Map, including the How to Use the Maps and Map Creation pages.
• Virginia Cooperative Extension (Virginia Tech), Virginia’s Home Garden Vegetable Planting Guide: Recommended Planting Dates and Amounts to Plant (426-331).
• Colorado State University Extension, Vegetable Planting Guide.
• Purdue Extension, Starting Seeds Indoors (HO-14-W).