In Arizona, the last spring frost usually comes between January 18 and May 17, and the first fall frost between October 5 and December 16, depending on where you live. Most of Arizona is in USDA hardiness zones 6b to 10a.
Find the frost dates for your ZIP code
Frost dates from NOAA 1991–2020 U.S. Climate Normals, nearest weather station. Zones derived from the 2023 USDA Plant Hardiness Zone Map data (PRISM Climate Group, Oregon State University). This is not the official USDA Plant Hardiness Zone Map.
Frost dates for Arizona cities
Dates come from the NOAA weather station closest to each city. The last spring frost and first fall frost are the typical dates, with a 30% chance of frost after (or before) them. The safer planting date has only a 10% chance of a later spring frost: use it for tender plants like tomatoes, peppers and basil.
| City | Zone | Last frost | Safer date | First frost |
|---|---|---|---|---|
| Phoenix | 10a | Jan. 9 | Jan. 22 | Dec. 30 |
| Tucson | 9b | Feb. 2 | Feb. 18 | Dec. 9 |
| Yuma | 10a | Jan. 31 | Feb. 19 | Dec. 21 |
| San Tan Valley | 9b | Feb. 12 | Feb. 27 | Dec. 3 |
| Flagstaff | 6a | June 10 | June 19 | Sep. 23 |
| Lake Havasu City | 10a | Jan. 15 | Feb. 3 | Dec. 21 |
| Casa Grande | 9a | Feb. 17 | Feb. 28 | Nov. 29 |
| Buckeye | 9b | Jan. 18 | Feb. 5 | Dec. 16 |
| Sierra Vista | 8b | March 31 | April 12 | Nov. 14 |
| Prescott Valley | 7b | May 6 | May 15 | Oct. 15 |
Frost dates vary a lot across Arizona. Among the cities above, Phoenix has the earliest last frost (around January 9) and Flagstaff the latest (around June 10), about 22 weeks apart. Elevation, nearby water and local terrain all make a difference, so use the dates for the place closest to you, or look up your ZIP code.
Growing zones in Arizona
Most of Arizona is in USDA hardiness zones 6b to 10a. A typical frost-free growing season lasts about 296 days, longer in the warmest areas and shorter in the coldest.
Find planting dates for the main zones in Arizona:
- Zone 6 (about 7% of ZIP codes): Tomatoes, Peppers, Potatoes, Lettuce, Green beans, Cucumbers, Garlic, Tulips
- Zone 7 (about 14% of ZIP codes): Tomatoes, Peppers, Potatoes, Lettuce, Green beans, Cucumbers, Garlic, Tulips
- Zone 8 (about 18% of ZIP codes): Tomatoes, Peppers, Potatoes, Lettuce, Green beans, Cucumbers, Garlic, Tulips
- Zone 9 (about 50% of ZIP codes): Tomatoes, Peppers, Potatoes, Lettuce, Green beans, Cucumbers, Garlic, Tulips
- Zone 10 (about 11% of ZIP codes): planting guides for this zone are coming soon.
See all crops in our planting guides, or build a planting calendar for your ZIP code.
How to use frost dates
- Cool-season crops such as peas, lettuce, spinach and onions can go in several weeks before your last spring frost.
- Warm-season crops such as tomatoes, peppers, squash and beans wait until after it, when the soil has warmed.
- Fall crops are timed back from your first fall frost, and garlic and tulips are planted around it.
- Frost dates are averages. Check the forecast before setting out tender plants.
Frequently asked questions
When is the last frost in Arizona?
It depends on where you live. Across most of Arizona, the last spring frost comes between January 18 and May 17. In Phoenix, it is around January 9.
When is the first frost in Arizona?
Across most of Arizona, the first fall frost comes between October 5 and December 16. In Phoenix, it is around December 30.
What planting zone is Arizona?
Most of Arizona is in USDA hardiness zones 6b to 10a. Enter your ZIP code above to find your exact zone.
When can I plant tomatoes in Arizona?
Plant tomatoes outside after your last frost, once nights stay above 50 °F. In Phoenix, the safer date, with only a 10% chance of a later frost, is around January 22. See our tomato planting guide.
Sources. Frost dates come from the nearest NOAA weather station to each city or ZIP code. Zones come from the 2023 USDA Plant Hardiness Zone Map ZIP code data. Our zone lookup is not the official USDA map.