Fall in zone 8bPhoto: George Chernilevsky, Public domain, via Wikimedia Commons
Frost dates for ZIP 85646 (Tubac, AZ)
Average last spring and first fall frost dates with 10%, 50% and 90% odds, from NOAA's 1991–2020 climate normals for the nearest weather station, Tumacacori Nm, AZ (4 miles away).
- Average last spring frostApr 550% chance of a 32°F freeze after this date
- Average first fall frostNov 1050% chance of a 32°F freeze by this date
- Growing season (frost-free)217 daysmedian, 32°F threshold
- USDA hardiness zone8b15 to 20°F avg. coldest night
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This week in your yard
As of Oct 18, 2026, from your frost dates, zone and soil temperature. Lawn timing · Vegetables · Pruning · Plants
Soil temperature now
2-inch depth
68°F 55°F or warmer
24-hour average · latest 66°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Elgin 5 S (32 mi), Tucson 11 W (43 mi), Walnut Gulch #1 (59 mi).
4-inch depth
69°F 55°F or warmer
24-hour average · latest 69°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Elgin 5 S (32 mi), Tucson 11 W (43 mi), Walnut Gulch #1 (59 mi).
Fall: Texas A&M AgriLife times fall pre-emergent (for winter weeds such as annual bluegrass) to soil cooling to about 70°F for several days. The 50–55°F band is the spring trigger. Always read and follow the product label.
7-day forecast and frost risk
The latest National Weather Service 7-day forecast and any Frost Advisory or Freeze Warning for 85646 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 69°F at 4 inches (estimated soil temperature, not a station reading). Fall pre-emergent (annual bluegrass, winter weeds): window open as soil cools through the 70s and 60s.
Fertilizer window
Lawn region: Arid Southwest (low desert). Timing only; always follow the product label.
- Bermudagrass (warm-season): Spring: Several weeks after the lawn is fully green (April–May) (about May 21 here, using green-up about 3–4 weeks after your average last frost); Summer: Every 4–6 weeks through mid-August (heaviest feeder of the group); Late: Light, low-nitrogen/high-potassium feeding about 4 weeks before first frost, or skip. Avoid: Heavy late-fall nitrogen (linked to spring dead spot).
- Perennial ryegrass (cool-season): Early fall: September; Late fall: October–November; Overseeded Bermuda: Light feeding once the winter rye is established, if needed. Avoid: Summer feeding.
Plant now
Prune now
No frost-timed pruning windows are open this week.
Your average first frost is Nov 10: skip heavy pruning in the 6–8 weeks before it, because new growth may not harden off in time.
Spring-flowering shrubs are pruned right after their flowers fade, not by date. See the pruning guide.
Last spring frost odds
| Chance of a 32°F freeze after this date | Date |
|---|---|
| 90% (early: most years still freeze after this) | Mar 13 |
| 50% (the "average" last frost) | Apr 5 |
| 10% (cautious: only 1 year in 10 freezes later) | Apr 25 |
Most gardeners plant frost-tender crops (tomatoes, peppers, basil) after the 50% date, and closer to the 10% date for less risk.
First fall frost odds
| Chance the first 32°F freeze has happened by this date | Date |
|---|---|
| 10% (early: 1 year in 10 freezes this soon) | Oct 21 |
| 50% (the "average" first frost) | Nov 10 |
| 90% (late: most years have frozen by now) | Nov 27 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | Apr 23 | Oct 30 |
| 32°F (freeze) | Apr 5 | Nov 10 |
| 28°F (hard freeze) | Mar 12 | Nov 20 |
n/a means NOAA did not publish a date at that threshold for this station (usually because it rarely gets that cold).
Vegetable planting calendar for 85646
Dates count from your average last spring frost (Apr 5) and first fall frost (Nov 10). Half of years have a frost after the spring date, so give tender crops (tomatoes, peppers, squash) some slack.
| Crop | Start indoors | Spring planting | Fall planting |
|---|---|---|---|
| Tomato | Feb 8–22 | Apr 12–26 (transplant) | Jul 14–Aug 11 (transplant) |
| Pepper (sweet and hot) | Jan 25–Feb 8 | Apr 19–May 3 (transplant) | Jul 21–Aug 11 (transplant) |
| Eggplant | Jan 25–Feb 8 | Apr 19–May 3 (transplant) | Jul 21–Aug 11 (transplant) |
| Tomatillo | Feb 8–22 | Apr 12–26 (transplant) | – |
| Lettuce | Feb 8–22 | Mar 15–Apr 5 (transplant) Mar 8–Apr 19 (sow outdoors) | Sep 15–Oct 6 (transplant) Sep 1–29 (sowing) |
| Spinach | – | Feb 22–Mar 15 (sow outdoors) | Sep 15–Oct 6 (sowing) |
| Kale | Feb 8–22 | Mar 8–22 (transplant) Mar 8–22 (sow outdoors) | Aug 18–Sep 15 (transplant) Aug 4–Sep 1 (sowing) |
| Collards | Feb 8–22 | Mar 8–Apr 5 (transplant) Mar 8–Apr 5 (sow outdoors) | Aug 18–Sep 15 (transplant) Aug 4–Sep 1 (sowing) |
| Broccoli | Jan 25–Feb 8 | Mar 8–22 (transplant) | Aug 4–Sep 1 (transplant) |
| Cabbage | Jan 25–Feb 8 | Mar 8–22 (transplant) | Aug 4–Sep 1 (transplant) |
| Cauliflower | Jan 25–Feb 8 | Mar 22–Apr 5 (transplant) | Aug 4–Sep 1 (transplant) |
| Brussels sprouts | Jan 11–25 | Mar 8–22 (transplant) | Jul 21–Aug 11 (transplant) |
| Kohlrabi | Feb 8–22 | Mar 8–22 (transplant) Mar 8–22 (sow outdoors) | Sep 1–15 (sowing) |
| Bok choy / Asian greens | – | Mar 8–22 (sow outdoors) | Sep 15–29 (sowing) |
| Arugula | – | Mar 8–Apr 5 (sow outdoors) | Sep 15–Oct 13 (sowing) |
| Mustard greens | – | Mar 8–29 (sow outdoors) | Sep 15–29 (sowing) |
| Swiss chard | Feb 22–Mar 8 | Mar 22–Apr 12 (transplant) Mar 22–Apr 19 (sow outdoors) | Sep 1–15 (sowing) |
| Beet | – | Mar 8–Apr 5 (sow outdoors) | Sep 1–15 (sowing) |
| Carrot | – | Mar 15–Apr 12 (sow outdoors) | Aug 18–Sep 1 (sowing) |
| Radish | – | Mar 1–Apr 12 (sow outdoors) | Sep 29–Oct 13 (sowing) |
| Turnip | – | Mar 8–29 (sow outdoors) | Sep 1–15 (sowing) |
| Parsnip | – | Mar 15–Apr 5 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Feb 8–Mar 8 (sow outdoors) | Aug 18–Sep 1 (sowing) |
| Onion (bulbing) | Jan 11–25 | Feb 22–Mar 8 (transplant) | – |
| Green onion / scallion | – | Feb 22–Mar 22 (sow outdoors) | Sep 1–15 (sowing) |
| Leek | Jan 11–25 | Mar 8–22 (transplant) | – |
| Garlic | – | – | Sep 29–Oct 27 (sowing) |
| Shallot | – | Feb 22–Mar 8 (transplant) | Sep 29–Oct 27 (sowing) |
| Potato | – | Mar 8–22 (transplant) | Jul 21–Aug 4 (transplant) |
| Sweet potato | – | Apr 26–May 10 (transplant) | – |
| Sweet corn | – | Apr 12–26 (sow outdoors) | – |
| Bean, bush (snap) | – | Apr 12–26 (sow outdoors) | Aug 18–Sep 1 (sowing) |
| Bean, pole | – | Apr 12–26 (sow outdoors) | – |
| Lima bean | – | Apr 19–May 3 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Apr 26–May 17 (sow outdoors) | – |
| Cucumber | Mar 8–15 | Apr 12–26 (transplant) Apr 12–26 (sow outdoors) | Aug 18–Sep 1 (sowing) |
| Summer squash / zucchini | Mar 8–15 | Apr 12–26 (transplant) Apr 12–26 (sow outdoors) | Aug 18–Sep 1 (sowing) |
| Winter squash | Mar 8–15 | Apr 12–26 (transplant) Apr 12–26 (sow outdoors) | – |
| Pumpkin | – | Apr 12–26 (sow outdoors) | – |
| Watermelon | Mar 8–15 | Apr 19–May 3 (transplant) Apr 19–May 3 (sow outdoors) | – |
| Cantaloupe / muskmelon | Mar 8–15 | Apr 19–May 3 (transplant) Apr 19–May 3 (sow outdoors) | – |
| Okra | Feb 22–Mar 8 | Apr 19–May 3 (transplant) Apr 19–May 3 (sow outdoors) | – |
| Celery | Jan 11–25 | Apr 12–19 (transplant) | – |
| Basil | Feb 22–Mar 8 | Apr 12–26 (transplant) Apr 12–26 (sow outdoors) | – |
| Cilantro | – | Mar 22–Apr 19 (sow outdoors) | Sep 15–29 (sowing) |
| Parsley | Jan 25–Feb 8 | Mar 22–Apr 5 (transplant) Mar 15–Apr 5 (sow outdoors) | – |
| Dill | – | Apr 5–19 (sow outdoors) | Sep 15–29 (sowing) |
| Sunflower | – | Apr 5–19 (sow outdoors) | – |
| Asparagus (crowns) | – | Mar 8–22 (transplant) | – |
| Rhubarb (crowns) | – | Mar 8–22 (transplant) | – |
| Strawberry (plants) | – | Mar 8–22 (transplant) | Sep 1–29 (transplant) |
Typical ranges from university extension planting calendars, adjusted to your frost dates. Probabilities, not guarantees. Fall windows that would overlap spring planting are left out, as are fall crops of frost-tender plants where the frost-free season is under 210 days.
Where these numbers come from
Station: Tumacacori Nm, AZ (NOAA GHCN-Daily ID USC00028865), elevation 3,267 ft, 3.7 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Nogales 6 N, AZ | 12 mi | Apr 16 | Nov 2 |
| Santa Rita EXP Range, AZ | 15 mi | Feb 25 | Dec 5 |
| Nogales Intl AP, AZ | 18 mi | Mar 20 | Nov 17 |
The average last-frost dates of these stations span 53 days, a rough guide to local variation. See data sources & methods.
Frost questions for 85646
When is the last frost in 85646?
The average (50% chance) last spring freeze of 32°F for ZIP 85646 is April 5. For a more cautious planting date, use April 25, when only 1 year in 10 still sees a later freeze.
When is the first frost in 85646?
The average first fall freeze is November 10. In 1 year in 10 it comes by October 21.
What hardiness zone is 85646?
ZIP 85646 is in USDA zone 8b (15 to 20°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 85646 right now?
This page shows the latest 2-inch and 4-inch soil temperature from the nearest public soil station (USDA SCAN, NOAA USCRN or TexMesonet), or a labeled estimate when no station is close, against the 50–55°F spring pre-emergent band.
Nearby ZIP codes
85640 Tumacacori-Carmen 85645 Elephant Head 85648 Rio Rico 85622 Green Valley 85614 Green Valley 85601 Arivaca 85621 Nogales 85624 Patagonia
Other ZIP codes in Santa Cruz County
85611 85621 85624 85637 85640 85648 All Santa Cruz County frost dates · Arizona frost dates
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Weekly yard timing, plus frost and soil-temperature alerts for your ZIP code.
- Freeze alerts
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Free. One weekly email plus alerts when your ZIP has a frost or a soil-temperature change worth acting on. After you submit, Kit (our email provider) sends a confirmation email: check your email and click the link to confirm. You aren't subscribed until you do. We collect only your email address and ZIP, sent to Kit to deliver The Dial. Unsubscribe anytime.