Rio Rico, AZ planting zone & frost dates
Rio Rico is in USDA hardiness zone 8b. The last spring frost usually comes around April 16 and the first fall frost around November 2, for a growing season of about 199 days.
Planting calendar for Rio Rico
Dates are counted from the average last spring frost (April 16) 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: Feb 19 – Mar 5 Transplant outdoors: Apr 23 – Apr 30 |
| Peppers | Start seeds indoors: Feb 5 – Feb 19 Transplant outdoors: Apr 30 – May 7 |
| Eggplant | Start seeds indoors: Feb 5 – Feb 19 Transplant outdoors: Apr 30 – May 7 |
| Broccoli | Start seeds indoors: Feb 5 – Feb 19 Transplant outdoors: Mar 19 – Apr 2 |
| Cabbage | Start seeds indoors: Feb 5 – Feb 19 Transplant outdoors: Mar 19 – Apr 2 |
| Onions (sets) | Plant outdoors: Mar 19 – Apr 2 |
| Peas | Sow outdoors: Mar 5 – Mar 19 |
| Spinach | Sow outdoors: Mar 5 – Mar 19 |
| Lettuce | Sow outdoors: Mar 19 – Apr 2 |
| Carrots | Sow outdoors: Mar 19 – Apr 2 |
| Potatoes | Plant outdoors: Mar 19 – Apr 2 |
| Beans | Sow outdoors: Apr 23 – Apr 30 |
| Sweet corn | Sow outdoors: Apr 23 – Apr 30 |
| Cucumbers | Sow outdoors: Apr 23 – Apr 30 |
| Squash & zucchini | Sow outdoors: Apr 23 – Apr 30 |
| Basil | Start seeds indoors: Mar 5 – Mar 19 Transplant outdoors: Apr 23 – Apr 30 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Sep 7 (8 weeks before the average first fall frost on Nov 2).
Useful for zone 8b 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
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Mar 28 | Apr 16 | May 4 |
| First 32°F frost in fall is before | Nov 16 | Nov 2 | Oct 19 |
How to read it: in spring there is a 10% chance of a frost after May 4, so that is a safe date for tender plants. In fall there is a 10% chance of frost before October 19. A hard freeze (28°F) usually ends around March 22.
Hardiness zone by ZIP code in Rio Rico
- 85648 zone 8b
Nearby cities
- Nogales zone 8b, last frost Mar 20
- Green Valley zone 9a, last frost Feb 25
- Sahuarita zone 9a, last frost Feb 25
- Vail zone 9a, last frost Jan 26
- Drexel Heights zone 9b, last frost Feb 5
- Sierra Vista zone 8b, last frost Apr 5
- Tucson Estates zone 9b, last frost Feb 8
- Tucson zone 9b, last frost Jan 20
Questions
What growing zone is Rio Rico, AZ?
Rio Rico is in USDA Plant Hardiness Zone 8b (average extreme winter low 15°F to 20°F), according to the USDA 2023 map.
When is the last frost in Rio Rico?
The average last spring frost (32°F) in Rio Rico is April 16. There is still a 10% chance of frost until May 4.
When can I plant tomatoes in Rio Rico?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Apr 23 – Apr 30. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Nogales 6 N, AZ (USC00025924), 2.0 km (1.2 mi) from the city center, elevation 1055 m, based on 19 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.