What growing zone am I in?
Your zone from the average coldest night of each winter, 1991 to 2020, at the NOAA weather station nearest you. Type a town and state or a postal code.
- Average winter low
- -5 to 0 °F
- Half zone
- b: the warmer half
- Last spring frost
- Apr 18
- First fall frost
- Oct 27
Average of each winter's lowest temperature, 1991-2020, station 6 mi away. Not the official USDA map.
How a zone is worked out
Every winter has one coldest night. Take that lowest temperature for each of the 30 winters from 1991 to 2020 and average them: that number sets the zone. Zones run in steps of 10 °F, from zone 1 below -50 °F to zone 13 above 60 °F, and each zone splits into a colder half (a) and a warmer half (b). Columbus, OH averages a winter low of -5 to 0 °F, which is zone 6b.
The zone answers one question: will a plant that lives for years survive the winter here? A shrub labeled for zones 5 to 8 should come through an average winter in zone 6b. It says nothing about summer heat, rain or soil, and it is not a planting date. For dates, use your frost dates.
Every zone at a glance
| Zone | Average winter low | Typical last frost | Typical first frost | Biggest cities |
|---|---|---|---|---|
| 3b | -35 to -30 °F | May 17 | Sep 26 | Hibbing, MN; Bemidji, MN; Brainerd, MN |
| 4a | -30 to -25 °F | May 16 | Sep 26 | Bismarck, ND; St. Cloud, MN; Grand Forks, ND |
| 4b | -25 to -20 °F | May 5 | Oct 5 | Anchorage, AK; Fargo, ND; Lakeville, MN |
| 5a | -20 to -15 °F | Apr 30 | Oct 9 | Minneapolis, MN; St. Paul, MN; Madison, WI |
| 5b | -15 to -10 °F | Apr 28 | Oct 16 | Omaha, NE; Lincoln, NE; Des Moines, IA |
| 6a | -10 to -5 °F | Apr 24 | Oct 20 | Chicago, IL; Denver, CO; Milwaukee, WI |
| 6b | -5 to 0 °F | Apr 20 | Oct 24 | Columbus, OH; Indianapolis, IN; Detroit, MI |
| 7a | 0 to 5 °F | Apr 14 | Oct 27 | Boston, MA; Louisville, KY; Wichita, KS |
| 7b | 5 to 10 °F | Apr 3 | Nov 2 | New York, NY; Philadelphia, PA; Oklahoma City, OK |
| 8a | 10 to 15 °F | Mar 27 | Nov 7 | Charlotte, NC; Washington, DC; Memphis, TN |
| 8b | 15 to 20 °F | Mar 16 | Nov 14 | Dallas, TX; Fort Worth, TX; El Paso, TX |
| 9a | 20 to 25 °F | Mar 3 | Nov 23 | San Antonio, TX; Austin, TX; Seattle, WA |
| 9b | 25 to 30 °F | Jan 31 | Dec 9 | Houston, TX; Jacksonville, FL; Tucson, AZ |
| 10a | 30 to 35 °F | Jan 14 | Dec 18 | Phoenix, AZ; San Jose, CA; Sacramento, CA |
| 10b | 35 to 40 °F | Jan 24 | Dec 19 | San Diego, CA; Long Beach, CA; Anaheim, CA |
| 11a | 40 to 45 °F | frost rare | frost rare | Los Angeles, CA; Miami, FL; Hialeah, FL |
Typical frost dates: the middle value among towns of 10,000 people or more in each zone (NOAA 1991-2020). Towns in the same zone can differ by two weeks or more.
Zones of 40 big cities
| City | Zone | City | Zone |
|---|---|---|---|
| New York, NY | 7b | Washington, DC | 8a |
| Los Angeles, CA | 11a | El Paso, TX | 8b |
| Chicago, IL | 6a | Las Vegas, NV | 8b |
| Houston, TX | 9b | Boston, MA | 7a |
| Phoenix, AZ | 10a | Detroit, MI | 6b |
| Philadelphia, PA | 7b | Louisville, KY | 7a |
| San Antonio, TX | 9a | Portland, OR | 9a |
| San Diego, CA | 10b | Memphis, TN | 8a |
| Dallas, TX | 8b | Baltimore, MD | 7b |
| Jacksonville, FL | 9b | Milwaukee, WI | 6a |
| Fort Worth, TX | 8b | Albuquerque, NM | 8a |
| San Jose, CA | 10a | Tucson, AZ | 9b |
| Austin, TX | 9a | Fresno, CA | 9b |
| Charlotte, NC | 8a | Sacramento, CA | 10a |
| Columbus, OH | 6b | Atlanta, GA | 8a |
| Indianapolis, IN | 6b | Mesa, AZ | 9b |
| Seattle, WA | 9a | Kansas City, MO | 6b |
| Denver, CO | 6a | Raleigh, NC | 8a |
| Oklahoma City, OK | 7b | Colorado Springs, CO | 6a |
| Nashville, TN | 7b | Omaha, NE | 5b |
Questions
Is this the official USDA zone?
No. The official map is drawn from a gridded climate model. We apply the same rule, the average of each winter's coldest night from 1991 to 2020, to the records of the NOAA weather station nearest you. For most towns the result is the same zone or half a zone off.
What do a and b mean?
Each zone covers 10 °F of average winter low. The a half is the colder 5 °F, the b half the warmer 5 °F. Zone 6a averages -10 to -5 °F, zone 6b -5 to 0 °F.
Does my zone tell me when to plant?
Only roughly. The zone is about winter cold, which decides which perennials, shrubs and trees survive. Planting dates for vegetables and annual flowers depend on your frost dates, which can differ by weeks within one zone.
Why did my zone change from an older map?
Older maps used the years 1976 to 2005. Winters in 1991 to 2020 were milder in much of the country, so many towns moved up half a zone.
Our own calculation from NOAA data: NOAA National Centers for Environmental Information, Global Summary of the Year, lowest temperature of each year (EMNT), 1991-2020, nearest station with at least 20 of the 30 years, up to 25 miles away. Not the official USDA Plant Hardiness Zone Map. Method.