Beginner's guide
USDA plant hardiness zones explained
Your USDA growing zone is a simple measure of winter cold. Gardeners use it mainly to check whether perennial plants are likely to survive winter in their location.
First, find your zone by ZIP Code
The official USDA map will give you a result such as Zone 7b. Return here to understand the number, the letter and what that result can tell you.
How to read your result
What does “Zone 7b” mean?
The number: 7
A 10°F winter band
Each numbered zone covers a 10°F range. Lower numbers indicate colder winters; higher numbers indicate warmer winters.
The letter: b
The warmer half
a is the colder 5°F half of a numbered zone. b is the warmer 5°F half.
The result: Zone 7b
5°F to 10°F
This is the range for the coldest temperature in a typical winter, not today's temperature.
In plain English: it measures long-term winter cold
For the 2023 map, USDA used 1991-2020 weather data. It averaged the lowest temperature reached in each year at a location. Your zone is not the current temperature, a normal winter average, the coldest temperature that can ever occur or your last spring frost date.
Complete USDA zone reference: 1a through 13b
You only need to find the one zone for your location. This complete list is available when you want to compare it with another zone or a plant label.
Green entries open a seed planner with Zone context.
Zone 1
Zone 2
Zone 3
Zone 4
Zone 5
Zone 6
Zone 6aColder half · -10°F to -5°FOpen seed plannerZone 6bWarmer half · -5°F to 0°FOpen seed plannerZone 7
Zone 7aColder half · 0°F to 5°FOpen seed plannerZone 7bWarmer half · 5°F to 10°FOpen seed plannerZone 8
Zone 9
Zone 10
Zone 11
Zone 12
Zone 13
Use your zone for perennial survival
Compare the zone range on a perennial plant's label with your location. Remember that wind, snow cover, drainage and small-scale temperature differences still matter.
Use frost dates for annual timing
Vegetable sowing and transplant dates depend more directly on local frost probabilities, soil temperature and current weather than on the hardiness-zone label.
Find first and last frost dates by ZIP CodeDo not use a hardiness zone as a frost calendar
The two measurements answer different questions. Use the comparison guide before choosing annual sowing or transplant dates.
Compare hardiness zones and frost dates →Your yard can contain smaller climate pockets
Use walls, slopes, shelter and repeated observations to understand variation that a national map cannot display.
Source: USDA Agricultural Research Service, 2023 USDA Plant Hardiness Zone Map ↗