Frost dates for 86547Round Rock, AZ
The average last spring frost in Round Rock is May 6 and the average first fall frost is October 8, giving a typical growing season of about 153 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 6
- Average first fall frost
- Oct 8
- Growing season
- 153 days
Safer after May 31 (1-in-10 risk)
Possible by Sep 26 (1-in-10 risk)
Last frost typically in 184 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | May 3 · May 21 · Jun 9 | Sep 20 · Oct 1 · Oct 14 | 132 days | 100% |
| Frost / freeze (32°F) | Apr 22 · May 6 · May 31 | Sep 26 · Oct 8 · Oct 23 | 153 days | 100% |
| Hard freeze (28°F) | Apr 8 · Apr 24 · May 12 | Oct 1 · Oct 18 · Nov 2 | 176 days | 100% |
Planting calendar for Round Rock
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Apr 5 – Jun 11 |
| Tomatoes | Transplant outdoors | May 22 – Jun 18 |
| Peppers | Start seeds indoors | Apr 5 – May 6 |
| Peppers | Transplant outdoors | Jun 5 – Jul 6 |
| Eggplant | Start seeds indoors | Apr 22 – May 21 |
| Eggplant | Transplant outdoors | Jun 5 – Jul 6 |
| Cucumbers | Sow outdoors | Jun 5 – Jun 28 |
| Summer squash | Sow outdoors | May 22 – Jul 6 |
| Winter squash & pumpkins | Sow outdoors | Jun 5 – Jul 6 |
| Snap beans | Sow outdoors | May 22 – Jul 21 |
| Sweet corn | Sow outdoors | May 22 – Jun 18 |
| Watermelon & cantaloupe | Sow outdoors | Jun 5 – Jul 6 |
| Okra | Sow outdoors | May 29 – Jun 21 |
| Peas | Sow outdoors (spring) | Apr 5 – May 21 |
| Potatoes | Plant outdoors (spring) | Apr 5 – Jun 5 |
| Onions | Start seeds indoors (spring) | Feb 22 – Mar 21 |
| Onions | Transplant outdoors (spring) | Apr 22 – May 21 |
| Broccoli | Start seeds indoors (spring) | Mar 18 – Apr 21 |
| Broccoli | Transplant outdoors (spring) | Apr 22 – May 21 |
| Broccoli | Start seeds indoors (fall) | Jun 8 – Jun 18 |
| Broccoli | Transplant outdoors (fall) | Jul 8 – Jul 19 |
| Cabbage | Start seeds indoors (spring) | Mar 8 – Apr 5 |
| Cabbage | Transplant outdoors (spring) | Apr 5 – May 6 |
| Cabbage | Start seeds indoors (fall) | May 29 – Jun 28 |
| Cabbage | Transplant outdoors (fall) | Jun 28 – Jul 29 |
| Leaf lettuce | Sow outdoors (spring) | Apr 5 – Jun 21 |
| Leaf lettuce | Sow outdoors (fall) | Jun 28 – Aug 14 |
| Spinach | Sow outdoors (spring) | Mar 29 – May 12 |
| Spinach | Sow outdoors (fall) | Jul 15 – Aug 19 |
| Radishes | Sow outdoors (spring) | Apr 5 – May 26 |
| Radishes | Sow outdoors (fall) | Jun 28 – Aug 29 |
| Kale | Sow outdoors (spring) | Apr 22 – May 12 |
| Kale | Sow outdoors (fall) | Jun 21 – Jul 29 |
| Carrots | Sow outdoors (spring) | May 6 – Jun 21 |
| Carrots | Sow outdoors (fall) | May 29 – Jul 14 |
| Garlic | Plant outdoors (fall) | Sep 28 – Oct 29 |
Where these dates come from
ZIP code 86547 is matched to the NOAA station Canyon De Chelly, AZ, 40.4 km away, at 5,610 ft elevation (256 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Canyon De Chelly, AZ (used) | 5,610 ft | May 6 | Oct 8 |
| Lukachukai, AZ | 6,520 ft | May 3 | Oct 17 |
| Teec Nos Pos, AZ | 5,290 ft | Apr 11 | Nov 1 |
| Monument Valley, AZ | 5,501 ft | Apr 10 | Nov 1 |
Frost dates near Round Rock
- Many Farms, AZ 86538 · last May 6, first Oct 8
- Lukachukai, AZ 86507 · last May 3, first Oct 17
- Rock Point, AZ 86545 · last Apr 11, first Nov 1
- Teec Nos Pos, AZ 86514 · last Apr 11, first Nov 1
- Tsaile, AZ 86556 · last May 3, first Oct 17
- Chinle, AZ 86503 · last May 6, first Oct 8
- Dennehotso, AZ 86535 · last Apr 10, first Nov 1
- Sanostee, NM 87461 · last May 3, first Oct 17
Frequently asked questions
- When is the last frost in Round Rock, AZ?
- For ZIP code 86547, the average last spring frost (32°F) is May 6, based on NOAA 1991-2020 climate normals for the Canyon De Chelly, AZ weather station. There is a 1-in-10 chance of a frost after May 31.
- When is the first frost in Round Rock, AZ?
- The average first fall frost (32°F) is October 8. There is a 1-in-10 chance of frost by September 26, so tender plants are at risk from that point on.
- How long is the growing season in 86547?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 153 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.