Planting Zone by ZIP Code: Find Your Zone and Frost Dates

Your planting zone tells you which perennials, trees, and shrubs can survive winter where you live. Your frost dates tell you when to plant vegetables. To find both, enter your ZIP code: you get your USDA plant hardiness zone from the 2023 USDA map and your average last spring and first fall frost dates from local weather station records.

Most beginners stop at the zone number. That number answers one question well: how cold does it get on the coldest night of a normal winter? It says nothing about when your tomatoes can go outside, and mixing up those two ideas is how many seedlings get lost to a late frost.

We garden in Zone 7b and use both numbers every season. The zone guides what we buy at the nursery. The frost dates guide when we plant.

Key Takeaways

• Your USDA zone predicts winter survival for plants that live year after year.
• Frost dates, not zones, set the timing for vegetables.
• Spots in your own yard can run warmer or colder than your official zone.

Enter your ZIP code in the tool below to see your planting zone and frost dates.

Building new beds for the season? Our raised bed soil calculator works out how much soil to buy.

How to Read Your ZIP Code Lookup Results

Your results show two kinds of information: a hardiness zone and a pair of frost dates. Each comes from a different data set and answers a different question, so it helps to know what you are looking at before you shop or plant.

Enter Your ZIP Code and Check Your Zone and Frost Dates

Type your five-digit ZIP code into the tool. You will see a zone label such as “7b,” plus an average last spring frost date and an average first fall frost date.

Read them in this order:

1. Zone: Use this when buying perennials, trees, shrubs, and bulbs. Plant tags list a zone range, such as “Zones 4 to 8.” Your zone should fall inside that range.
2. Last spring frost: Use this to time when tender vegetables and annual flowers go outside.
3. First fall frost: Use this to count backward for fall crops and to know when your warm-season plants will quit.

The days between the two frost dates make up your average frost-free growing season.

Which Data Does Our Lookup Use?

Our lookup uses USDA 2023 Plant Hardiness Zone Map data matched to ZIP codes. That map is the current USDA planting zone map, built by the USDA Agricultural Research Service and Oregon State University’s PRISM Climate Group.

Frost dates come from NOAA 1991 to 2020 weather station averages, known as the U.S. Climate Normals. These are 30-year averages, so they describe a typical year. Any single spring can come early or late.

Why Can One ZIP Code Include Different Zones?

ZIP codes are drawn for mail delivery, while USDA plant hardiness zones follow temperature. A single ZIP code can cross hills, valleys, rivers, or the edge of a city, and each of those changes how cold the nights get.

The 2023 map is detailed enough to show these shifts. It uses data from 13,412 weather stations, compared with 7,983 for the 2012 map. Lookups by ZIP code show one zone for the area as a whole, so if you live near a ridge or valley, your own yard may sit half a zone off.

What Does Your USDA Zone Tell You About Plant Survival?

Your USDA hardiness zone tells you how cold your winters get on average, which predicts whether a plant can live through them. It is a cold-survival rating only, built from 30 years of the coldest winter nights.

How Winter Temperatures Define Zones and Half-Zones

Plant hardiness zones are based on the average annual minimum winter temperature. Think of it as the coldest night of each year, averaged over 1991 to 2020. It is not the coldest night ever recorded.

The map has 13 zones across the United States and its territories. Each zone covers 10°F. Each zone splits into an “a” half and a “b” half of 5°F each, and “a” is always the colder half.

Our Zone 7b, for example, averages a coldest night between 5°F and 10°F.

What Is the Difference Between Zone 6a and Zone 6b?

Zone 6 covers an average coldest night of -10°F to 0°F.

• Zone 6a: -10°F to -5°F
• Zone 6b: -5°F to 0°F

Five degrees sounds small. For a plant right at its limit, it decides whether roots and buds survive. A shrub rated “Zone 6” may do fine in 6b and struggle in 6a during a hard winter. When a plant tag lists only full zones, gardeners in the “a” half should give it a sheltered spot.

Why Did Many Zones Change on the 2023 Map?

The 2023 USDA plant hardiness zone map was the first update since 2012. About half of the country moved to the next warmer half zone. The other half stayed the same.

Most changes came from using newer weather data (1991 to 2020) and more stations. Better mapping methods played a part too. The USDA cautions against reading these shifts as a direct measure of climate change, because the coldest night of the year jumps around a lot from one winter to the next.

If your zone changed, plants you already own did not get tougher. Treat the new zone as a better picture of a normal winter.

How to Choose Perennials, Trees, and Shrubs

Perennials, trees, and shrubs face every winter, so the zone matters most for them. Here is how we use it at the garden center:

1. Check that your zone sits inside the range on the tag.
2. For long-lived trees, pick plants rated at least one half zone colder than yours. A tree lives through decades of winters, including a few harsh ones.
3. Look for “hardy to” temperatures on tags. Compare them with your zone’s range.
4. Use plant guides from your state’s university extension service, which test plants in local conditions.

Annual vegetables and flowers live one season, so their zone rating barely matters. Timing matters for them instead.

What Hardiness Zones Cannot Tell You

Zones measure cold only. They leave out:

• Summer heat and humidity
• Rainfall and drought
• Soil type, drainage, and pH
• Sun and shade
• How long winter lasts, or how often it swings warm and cold

Two places can share Zone 7b and still need very different plants. A dry, hot-summer area and a wet, mild-summer area grow different things well. Read plant tags for sun, water, and soil needs along with the zone.

When Should You Plant Vegetables Using Frost Dates?

Plant vegetables by your frost dates and soil temperature, not your zone. Frost dates tell you when freezing nights end in spring and start again in fall, and that window controls your vegetable season.

Why Frost Dates Matter More Than Zones for Vegetable Timing

Planting zones describe the coldest winter night. Vegetables grow in spring, summer, and fall, so winter lows don’t affect them. A frost of 32°F in May can kill a tomato no matter what zone you live in.

Two places in the same zone can have last frost dates weeks apart, which is why our lookup shows both numbers. If you are new to vegetables, our guide on starting your own garden as a beginner covers soil and bed setup to pair with these dates.

Average Last Spring Frost vs. a Safer Planting Date

The average last spring frost is the date when the chance of another freeze drops below 50%. On that date, you still have about a coin-flip chance of one more frost. That is too risky for tender plants.

NOAA also tracks the date when the chance falls below 10%. That is a much safer date for warm-season crops. In one NOAA example for Boulder, Colorado, the 50% date was May 6 and the 10% date was May 18, about 12 days later.

A practical plan:

• Cool-season crops like peas, spinach, lettuce, and radishes can be direct-seeded when soil reaches 40°F to 50°F, often weeks before the last frost.
• Warm-season crops like tomatoes, peppers, eggplant, and basil need soil of 50°F to 60°F. Plant them after the last frost, closer to the 10% date.
• Watch the 10-day forecast and keep frost cloth or old sheets handy.

How First Fall Frost Shapes Your Growing Season

The first fall frost ends the season for tender crops. Bush snap beans take 45 to 65 days to mature, and a light frost of 30°F to 32°F kills them. Kale takes about as long but survives down to about 20°F.

To plant a fall crop, count back from your first fall frost date using the days to maturity on the seed packet. Add one to two weeks, since growth slows as days get shorter and cooler. Cold-hardy picks like kale, cabbage, collards, and spinach give you more room for error.

Build a Planting Schedule Around Each Crop

A good planting schedule lists each crop with its own start date. Here is how to build one:

1. Write down your last spring frost and first fall frost.
2. Sort crops into cool-season and warm-season groups.
3. For seeds started indoors, count back the weeks listed on the packet from your last frost date.
4. Set warm-season transplant dates after your last frost.
5. Count back from the first fall frost for late crops.
6. Plant leafy greens every few weeks for a steady harvest.

Herbs fit into the same plan. Basil is killed by frost, while chives and thyme handle cool weather; our notes on how to start your own herb garden cover which herbs go out early.

How Can Microclimates Change Conditions in Your Yard?

Microclimates are small spots that run warmer or colder than the USDA hardiness zones around them, sometimes by a full half zone. Walls, pavement, slopes, and low ground all change how cold a given patch gets at night.

South-Facing Walls and Urban Warmth

A south-facing wall soaks up sun all day and gives off heat at night. Beds against it warm up earlier in spring and stay frost-free longer in fall. These are good spots for early lettuce, late peppers, or a perennial rated slightly too warm for your zone.

Cities run warmer than the countryside around them. Pavement, buildings, and traffic hold heat, so urban yards often get later fall frosts and milder winter lows than the official numbers suggest.

Low Spots Where Cold Air Collects

Cold air is heavy and flows downhill like water. It pools in low corners, at the bottom of slopes, and behind solid fences. These frost pockets can freeze on nights when the rest of the yard stays above 32°F.

To spot one, walk your yard on a clear, still morning after a cold night. Frosty grass in one area and dry grass in another shows you where cold settles. Keep tender plants and early-blooming fruit trees out of those spots.

How to Garden Near a Zone Boundary

Near a zone line, plan for the colder side for anything permanent. Choose trees and shrubs that fit both zones, and save borderline plants for warm, sheltered spots.

A cheap min/max thermometer placed in different areas of your yard tells you a lot over one winter. Mulch the roots of borderline perennials in late fall, and plant them near walls or other buildings where plant hardiness gets a small boost.

Choose Plants by Zone and Plant by Local Conditions

Use your planting zone to decide what to grow, and use your frost dates to decide when to grow it. Each number does one job well.

When you buy perennials, trees, and shrubs, match the tag to your zone. For anything meant to last decades, lean one half zone colder. Remember the 2023 map moved about half the country a half zone warmer, so older tags and books may list your area differently.

For vegetables, build your planting schedule from frost dates and soil temperature:

• Seed cool-season crops when soil hits 40°F to 50°F.
• Hold tender crops until the danger of frost has passed, aiming near the 10% date.
• Count back from your first fall frost for late crops.

Then check your yard itself. South walls and city heat buy you a few extra days. Low spots and open slopes take them away. In our Zone 7b garden, we treat the lookup numbers as the starting point and the morning frost on the grass as the final word on where tender plants go.

Planting Schedules by Zone

• Zone 7a planting schedule (last frost about Apr 16)
• Zone 7b planting schedule (last frost about Apr 6)

Frequently Asked Questions