When Is the Last Frost in Arizona?
The average last spring frost in Arizona falls between January 7 and May 11 for most ZIP codes, with a statewide median of February 18. At the average date a later frost is still a coin flip, so tender plants wait for the safer 90% date.
| City | Last frost | 90% safe after | First frost | Growing season |
|---|---|---|---|---|
| Phoenix | Jan 8 | Feb 12 | Dec 25 | 354 days |
| Tucson | Feb 5 | Mar 2 | Dec 9 | 307 days |
| Mesa | Feb 1 | Feb 28 | Dec 10 | 312 days |
| Gilbert | Feb 1 | Feb 27 | Dec 11 | 315 days |
| Chandler | Feb 1 | Feb 27 | Dec 11 | 315 days |
| Glendale | Jan 20 | Feb 18 | Dec 15 | 331 days |
| Scottsdale | Jan 27 | Mar 5 | Dec 21 | 330 days |
| Peoria | Feb 5 | Mar 3 | Dec 11 | 306 days |
| Tempe | Feb 13 | Mar 9 | Dec 5 | 298 days |
| Surprise | Feb 5 | Mar 3 | Dec 11 | 306 days |
| Goodyear | Jan 7 | Feb 5 | Dec 24 | 351 days |
| Buckeye | Jan 7 | Feb 5 | Dec 24 | 351 days |
| Yuma | Jan 8 | Feb 19 | Dec 28 | 362 days |
| Flagstaff | Jun 4 | Jun 19 | Sep 28 | 115 days |
| Maricopa | Feb 23 | Mar 15 | Nov 24 | 274 days |
| Casa Grande | Feb 5 | Feb 28 | Dec 6 | 305 days |
| Marana | Apr 2 | Apr 18 | Nov 11 | 222 days |
| Lake Havasu Cityfrost in <50% of winters | Jan 5 | Feb 3 | Dec 29 | 365 days |
| Sierra Vista | Mar 16 | Apr 12 | Nov 21 | 246 days |
| Douglas | Mar 18 | Apr 12 | Nov 13 | 235 days |
| Show Low | May 5 | May 20 | Oct 15 | 162 days |
| Pinetop-Lakeside | May 22 | Jun 4 | Oct 6 | 138 days |
Last and first frost: 50% (median) dates of the last spring and first fall 32 °F night. 90% safe after: only a 10% chance of a later spring frost. First frost dates in January fall in the following winter. Each city uses the NOAA station nearest the ZIP code closest to its center.
Across all 174 Arizona weather stations with frost records, median last frost dates run from January 4 at Bullhead City, AZ to June 23 at Flagstaff 4 SW, AZ. Elevation, valleys that collect cold air and distance from large water bodies explain most of the spread, so a garden a few miles from a listed city can differ by a week or more. The ZIP code lookup above uses the same NOAA data as the frost date calculator for every US ZIP code.
When Is the First Frost in Arizona?
The average first fall frost in Arizona arrives between October 10 and December 25 for most ZIP codes, with a median of December 2. Tomatoes, peppers, basil and squash are damaged at 32 °F, so harvest or cover them before then.
Fall frost can come early: Phoenix has a 10% chance of frost before December 5, Tucson has a 10% chance of frost before November 21 and Mesa has a 10% chance of frost before November 22. Hardy crops such as kale, spinach and cabbage tolerate light frosts and keep producing after the first frost date.
When to Plant Tomatoes in Arizona?
Transplant tomatoes in Arizona 1 to 2 weeks after the local average last frost, once nights stay above about 50 °F: Jan 15 – Jan 22 in Phoenix, Feb 12 – Feb 19 in Tucson and Feb 8 – Feb 15 in Mesa. Start seeds indoors 6 to 8 weeks before the last frost.
| City | Start seeds indoors | Transplant outdoors | Lowest-risk transplant |
|---|---|---|---|
| Phoenix | Nov 13 – Nov 27 | Jan 15 – Jan 22 | after Feb 12 |
| Tucson | Dec 11 – Dec 25 | Feb 12 – Feb 19 | after Mar 2 |
| Mesa | Dec 7 – Dec 21 | Feb 8 – Feb 15 | after Feb 28 |
| Gilbert | Dec 7 – Dec 21 | Feb 8 – Feb 15 | after Feb 27 |
| Chandler | Dec 7 – Dec 21 | Feb 8 – Feb 15 | after Feb 27 |
| Glendale | Nov 25 – Dec 9 | Jan 27 – Feb 3 | after Feb 18 |
| Scottsdale | Dec 2 – Dec 16 | Feb 3 – Feb 10 | after Mar 5 |
| Peoria | Dec 11 – Dec 25 | Feb 12 – Feb 19 | after Mar 3 |
| Tempe | Dec 19 – Jan 2 | Feb 20 – Feb 27 | after Mar 9 |
| Surprise | Dec 11 – Dec 25 | Feb 12 – Feb 19 | after Mar 3 |
| Goodyear | Nov 12 – Nov 26 | Jan 14 – Jan 21 | after Feb 5 |
| Buckeye | Nov 12 – Nov 26 | Jan 14 – Jan 21 | after Feb 5 |
| Yuma | Nov 13 – Nov 27 | Jan 15 – Jan 22 | after Feb 19 |
| Flagstaff | Apr 9 – Apr 23 | Jun 11 – Jun 18 | after Jun 19 |
| Maricopa | Dec 29 – Jan 12 | Mar 2 – Mar 9 | after Mar 15 |
| Casa Grande | Dec 11 – Dec 25 | Feb 12 – Feb 19 | after Feb 28 |
| Marana | Feb 5 – Feb 19 | Apr 9 – Apr 16 | after Apr 18 |
| Lake Havasu City | Nov 10 – Nov 24 | Jan 12 – Jan 19 | after Feb 3 |
| Sierra Vista | Jan 19 – Feb 2 | Mar 23 – Mar 30 | after Apr 12 |
| Douglas | Jan 21 – Feb 4 | Mar 25 – Apr 1 | after Apr 12 |
| Show Low | Mar 10 – Mar 24 | May 12 – May 19 | after May 20 |
| Pinetop-Lakeside | Mar 27 – Apr 10 | May 29 – Jun 5 | after Jun 4 |
Indoors: 6–8 weeks before the average last frost. Outdoors: 1–2 weeks after it. Lowest-risk: after the date with only a 10% chance of a later frost. Rules of thumb; check the 10-day forecast and wait for soil near 60 °F.
Tomatoes stall below about 50 °F at night and are killed by frost, so a week or two of waiting after the average date costs little. The tomato plant care guide covers light, watering and feeding once plants are in the ground. In frost-free or rare-frost areas such as Lake Havasu City, summer heat limits tomatoes more than frost: flowers often drop without setting fruit when nights stay above about 75 °F, so gardeners there typically plant in late winter and again for a fall crop.
What Can You Plant in Phoenix and When?
Phoenix's average last frost of January 8 anchors its spring planting calendar: peas and spinach go in from November 27, broccoli and lettuce transplants from December 11, and tomatoes, peppers and squash after January 15.
| Crop | Start seeds indoors | Plant outdoors | Frost tolerance |
|---|---|---|---|
| Peas | — | Nov 27 – Dec 11direct sow, 4–6 weeks before last frost | hardy |
| Spinach | — | Nov 27 – Dec 18direct sow, 3–6 weeks before last frost | hardy |
| Radishes | — | Dec 4 – Dec 18direct sow, 3–5 weeks before last frost | hardy |
| Onions (sets) | — | Dec 11 – Dec 25plant, 2–4 weeks before last frost | hardy |
| Potatoes | — | Dec 11 – Dec 25plant, 2–4 weeks before last frost | half-hardy |
| Broccoli & cabbage | Nov 13 – Nov 27 | Dec 11 – Dec 25transplant, 2–4 weeks before last frost | hardy |
| Lettuce | Nov 27 – Dec 11 | Dec 11 – Dec 25transplant, 2–4 weeks before last frost | hardy |
| Beets | — | Dec 11 – Dec 25direct sow, 2–4 weeks before last frost | half-hardy |
| Carrots | — | Dec 18 – Dec 25direct sow, 2–3 weeks before last frost | half-hardy |
| Tomatoes | Nov 13 – Nov 27 | Jan 15 – Jan 22transplant, 1–2 weeks after last frost | tender |
| Basil | Nov 13 – Nov 27 | Jan 15 – Jan 29transplant, 1–3 weeks after last frost | tender |
| Peppers | Oct 30 – Nov 13 | Jan 22 – Jan 29transplant, 2–3 weeks after last frost | tender |
| Eggplant | Oct 30 – Nov 13 | Jan 22 – Jan 29transplant, 2–3 weeks after last frost | tender |
| Green beans | — | Jan 15 – Jan 29direct sow, 1–3 weeks after last frost | tender |
| Sweet corn | — | Jan 15 – Jan 29direct sow, 1–3 weeks after last frost | tender |
| Cucumbers | Dec 11 – Dec 18 | Jan 15 – Jan 29transplant, 1–3 weeks after last frost | tender |
| Squash & zucchini | Dec 11 – Dec 18 | Jan 15 – Jan 29transplant, 1–3 weeks after last frost | tender |
| Watermelon | Dec 11 – Dec 18 | Jan 22 – Jan 29transplant, 2–3 weeks after last frost | tender |
Dates for Phoenix (last frost Jan 8, NOAA station Phoenix Deer Valley Muni AP, AZ, 9 miles from ZIP 85021). General rules of thumb; wait for soil near 50 °F for most seeds and 60 °F for beans, corn and squash.
How Long Is the Growing Season in Arizona?
The frost-free growing season in Arizona lasts about 149 to 354 days for most ZIP codes, with a median of 287 days. Among the listed cities, Flagstaff has the shortest season at 115 days and Lake Havasu City the longest at 365.
Season length decides which varieties ripen: compare it with the “days to maturity” on seed packets, counted from transplanting for tomatoes and peppers. NOAA stations in Arizona range from 81 days at Flagstaff 4 SW, AZ to 365 days at Kofa Mine, AZ. Planning beds before the season starts helps in short seasons — a plant spacing calculator for vegetable beds shows how many transplants fit.
What Hardiness Zones Are in Arizona?
Arizona spans USDA hardiness zones 5b to 10a, with zone 9b the most common. Zones describe winter cold and decide which perennials survive, while frost dates set when to plant annual vegetables and flowers.
The Arizona planting zone map with the zone of each city shows how the zones are spread across the state and which plants are hardy in all of them.
Frequently Asked Questions
- When is the last frost in Arizona?
- The average last spring frost in Arizona falls between January 7 and May 11 for most ZIP codes, with a statewide median of February 18. Among major cities it ranges from January 5 in Lake Havasu City to June 4 in Flagstaff.
- When is the last frost in Phoenix, Arizona?
- Phoenix's average last spring frost is January 8, and by February 12 the chance of a later frost drops to 10%. Its first fall frost averages December 25, giving a 354-day growing season (NOAA station Phoenix Deer Valley Muni AP, AZ).
- When should you plant tomatoes in Arizona?
- Transplant tomatoes in Arizona 1 to 2 weeks after the local average last frost, once nights stay above about 50 °F: Jan 15 – Jan 22 in Phoenix, Feb 12 – Feb 19 in Tucson and Feb 8 – Feb 15 in Mesa. Start seeds indoors 6 to 8 weeks before the last frost.
- When is the first frost in Arizona?
- The average first fall frost in Arizona arrives between October 10 and December 25 for most ZIP codes, with a median of December 2. Harvest tender crops such as tomatoes, peppers and basil before then or cover them on cold nights.
- How long is the growing season in Arizona?
- The frost-free growing season in Arizona lasts about 149 to 354 days for most ZIP codes, with a median of 287 days, from 115 days in Flagstaff to 365 days in Lake Havasu City.
Frost data: NOAA National Centers for Environmental Information, 1991–2020 U.S. Climate Normals (32 °F freeze dates by probability). ZIP code and city locations and populations: U.S. Census Bureau Gazetteer files and Vintage 2024 population estimates. Planting windows are general rules of thumb. PlantoScan is not affiliated with or endorsed by these agencies.