What zone 9b means for Tempe
Hardiness zones are based on the average of the coldest night of each winter over 30 years (1991 to 2020). In zone 9b, that average is 25 to 30°F (-4 to -1°C). Plants labeled hardy to zone 9b or colder should survive a typical Tempe winter. A plant rated only to a warmer zone will need a sheltered spot, a pot you can bring inside, or treating as an annual.
Not every part of Tempe is the same: its ZIP codes fall in zones 9b, 10a. Check your own ZIP code in the table below.
How Tempe compares with the rest of Arizona
Arizona runs from zone 5b to zone 10a on the 2023 map. About 39% of the state's ZIP codes share Tempe's zone 9b. Gardeners in colder parts of the state may need hardier plants, while those in warmer parts can grow some plants that would struggle here.
Frost dates in Tempe
These are the median dates of the last and first 32°F freeze from NOAA's 1991 to 2020 climate normals, using the weather station closest to Tempe (Tempe Asu, about 1 km away). Half of years have a later last frost, so tender plants are safest a week or two after the date. Your own garden can differ with elevation and shelter: check your exact ZIP code above.
Vegetable planting calendar for Tempe
Purdue Extension groups vegetables by how much frost they can take and times planting from the average last spring frost. Applied to Tempe's last frost of February 13:
| Group | Plant outdoors | Crops |
|---|---|---|
| Hardy crops (tolerate a hard frost) 4 to 6 weeks before the average last spring frost | January 2 to January 16 | Asparagus, broccoli, Brussels sprouts, cabbage, collards, horseradish, kale, kohlrabi, leek, mustard, onion, peas, potato, radish, rhubarb, spinach, turnip |
| Semi-hardy crops (tolerate a light frost) 2 to 4 weeks before the average last spring frost | January 16 to January 30 | Beet, carrot, cauliflower, celery, chard, Chinese cabbage, lettuce, mustard, parsnip |
| Tender crops (damaged by frost) after the average last spring frost, once nights stay above 50°F | From February 13 | Bean, sweet corn, tomato |
| Very tender crops (warm season) at least 2 weeks after the average last spring frost, once nights stay above 60 to 65°F | From February 27 | Cucumber, eggplant, melons, okra, pepper, pumpkin, squash, sweet potato |
Spring planting for direct seeding or transplants. A late cold snap can still happen, so watch the forecast and protect tender plants. Want today's answer for your ZIP code? Use what to plant now.
Sources: NOAA NCEI U.S. Climate Normals 1991 to 2020; Purdue Extension, Indiana Vegetable Planting Calendar (HO-186-W).
Choosing plants for zone 9b
When you shop, look for the hardiness range on the tag or in the catalog, such as "zones 4 to 9". Pick perennials, shrubs and trees whose range includes 9b. If you are set on a plant rated only to a warmer zone, plant it in a sheltered spot against a south-facing wall, mulch the roots before winter, or grow it in a container you can move into a garage. Zones only cover winter cold, so also check sun, water and soil needs. More in how to read a plant tag.
Tempe ZIP codes and zones
ZIP codes GeoNames assigns to Tempe, which can include PO box ZIP codes.
Other cities in Arizona
Frequently asked questions
When is the last frost in Tempe?
The median last spring frost (32°F) near Tempe is February 13, and the median first fall frost is December 5, based on NOAA 1991 to 2020 climate normals.
What planting zone is Tempe in?
Tempe, AZ is in USDA plant hardiness zone 9b (ZIP codes range from 9b to 10a). Zone 9b means an average coldest winter night of 25 to 30°F (-4 to -1°C), based on the 2023 USDA map.
Did Tempe's zone change in 2023?
The 2023 USDA map uses weather data from 1991 to 2020. The USDA says about half of the country shifted to the next warmer half zone compared with the 2012 map, while the rest stayed in the same half zone.
Zones: 2023 USDA Plant Hardiness Zone Map ZIP code listings, PRISM Climate Group, Oregon State University. Place names: GeoNames (CC BY 4.0). Not the official USDA map. Our data.