San Tan Valley, AZ planting zone & frost dates
San Tan Valley is in USDA hardiness zone 9b. The last spring frost usually comes around February 1 and the first fall frost around December 11, for a growing season of about 315 days.
Planting calendar for San Tan Valley
Dates are counted from the average last spring frost (February 1) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Dec 7 – Dec 21 Transplant outdoors: Feb 8 – Feb 15 |
| Peppers | Start seeds indoors: Nov 23 – Dec 7 Transplant outdoors: Feb 15 – Feb 22 |
| Eggplant | Start seeds indoors: Nov 23 – Dec 7 Transplant outdoors: Feb 15 – Feb 22 |
| Broccoli | Start seeds indoors: Nov 23 – Dec 7 Transplant outdoors: Jan 4 – Jan 18 |
| Cabbage | Start seeds indoors: Nov 23 – Dec 7 Transplant outdoors: Jan 4 – Jan 18 |
| Onions (sets) | Plant outdoors: Jan 4 – Jan 18 |
| Peas | Sow outdoors: Dec 21 – Jan 4 |
| Spinach | Sow outdoors: Dec 21 – Jan 4 |
| Lettuce | Sow outdoors: Jan 4 – Jan 18 |
| Carrots | Sow outdoors: Jan 4 – Jan 18 |
| Potatoes | Plant outdoors: Jan 4 – Jan 18 |
| Beans | Sow outdoors: Feb 8 – Feb 15 |
| Sweet corn | Sow outdoors: Feb 8 – Feb 15 |
| Cucumbers | Sow outdoors: Feb 8 – Feb 15 |
| Squash & zucchini | Sow outdoors: Feb 8 – Feb 15 |
| Basil | Start seeds indoors: Dec 21 – Jan 4 Transplant outdoors: Feb 8 – Feb 15 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Oct 16 (8 weeks before the average first fall frost on Dec 11).
Useful for zone 9b gardens
- Seed starting kit with dome — to start seeds indoors before the last frost
- LED grow light for seedlings — stops leggy seedlings
- Frost cloth / plant covers — for late spring and early fall frosts
- Soil thermometer — warm-season crops need soil above 60°F
- Shade cloth — for hot summers
As an Amazon Associate, FrostZoneMap earns from qualifying purchases, at no extra cost to you.
Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Jan 2 | Feb 1 | Feb 27 |
| First 32°F frost in fall is before | Jan 1 | Dec 11 | Nov 23 |
How to read it: in spring there is a 10% chance of a frost after February 27, so that is a safe date for tender plants. In fall there is a 10% chance of frost before November 23. A hard freeze (28°F) usually ends around January 8.
Hardiness zone by ZIP code in San Tan Valley
- 85140 zone 9b
- 85143 zone 9b
Nearby cities
- Queen Creek zone 9b, last frost Feb 1
- Gold Canyon zone 9b, last frost Feb 11
- Florence zone 9a, last frost Jan 30
- Coolidge zone 9a, last frost Feb 17
- Apache Junction zone 9b, last frost Feb 11
- Gold Camp zone 9b, last frost Jan 18
- Gilbert zone 9b, last frost Feb 13
- Chandler zone 9b, last frost Feb 13
Questions
What growing zone is San Tan Valley, AZ?
San Tan Valley is in USDA Plant Hardiness Zone 9b (average extreme winter low 25°F to 30°F), according to the USDA 2023 map.
When is the last frost in San Tan Valley?
The average last spring frost (32°F) in San Tan Valley is February 1. There is still a 10% chance of frost until February 27.
When can I plant tomatoes in San Tan Valley?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Feb 8 – Feb 15. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Chandler Heights, AZ (USC00021514), 14.4 km (8.9 mi) from the city center, elevation 434 m, based on 14 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.