Fall in zone 8bPhoto: George Chernilevsky, Public domain, via Wikimedia Commons
Frost dates for ZIP 85648 (Rio Rico, 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, Nogales 6 N, AZ (3 miles away).
- Average last spring frostApr 1650% chance of a 32°F freeze after this date
- Average first fall frostNov 250% chance of a 32°F freeze by this date
- Growing season (frost-free)199 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
67°F 55°F or warmer
24-hour average · latest 65°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Elgin 5 S (30 mi), Tucson 11 W (52 mi), Walnut Gulch #1 (58 mi).
4-inch depth
68°F 55°F or warmer
24-hour average · latest 68°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Elgin 5 S (30 mi), Tucson 11 W (52 mi), Walnut Gulch #1 (58 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 85648 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 68°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 Jun 1 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 2: 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 28 |
| 50% (the "average" last frost) | Apr 16 |
| 10% (cautious: only 1 year in 10 freezes later) | May 4 |
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 19 |
| 50% (the "average" first frost) | Nov 2 |
| 90% (late: most years have frozen by now) | Nov 16 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | May 2 | Oct 24 |
| 32°F (freeze) | Apr 16 | Nov 2 |
| 28°F (hard freeze) | Mar 22 | Nov 14 |
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 85648
Dates count from your average last spring frost (Apr 16) and first fall frost (Nov 2). 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 19–Mar 5 | Apr 23–May 7 (transplant) | – |
| Pepper (sweet and hot) | Feb 5–19 | Apr 30–May 14 (transplant) | – |
| Eggplant | Feb 5–19 | Apr 30–May 14 (transplant) | – |
| Tomatillo | Feb 19–Mar 5 | Apr 23–May 7 (transplant) | – |
| Lettuce | Feb 19–Mar 5 | Mar 26–Apr 16 (transplant) Mar 19–Apr 30 (sow outdoors) | Sep 7–28 (transplant) Aug 24–Sep 21 (sowing) |
| Spinach | – | Mar 5–26 (sow outdoors) | Sep 7–28 (sowing) |
| Kale | Feb 19–Mar 5 | Mar 19–Apr 2 (transplant) Mar 19–Apr 2 (sow outdoors) | Aug 10–Sep 7 (transplant) Jul 27–Aug 24 (sowing) |
| Collards | Feb 19–Mar 5 | Mar 19–Apr 16 (transplant) Mar 19–Apr 16 (sow outdoors) | Aug 10–Sep 7 (transplant) Jul 27–Aug 24 (sowing) |
| Broccoli | Feb 5–19 | Mar 19–Apr 2 (transplant) | Jul 27–Aug 24 (transplant) |
| Cabbage | Feb 5–19 | Mar 19–Apr 2 (transplant) | Jul 27–Aug 24 (transplant) |
| Cauliflower | Feb 5–19 | Apr 2–16 (transplant) | Jul 27–Aug 24 (transplant) |
| Brussels sprouts | Jan 22–Feb 5 | Mar 19–Apr 2 (transplant) | Jul 13–Aug 3 (transplant) |
| Kohlrabi | Feb 19–Mar 5 | Mar 19–Apr 2 (transplant) Mar 19–Apr 2 (sow outdoors) | Aug 24–Sep 7 (sowing) |
| Bok choy / Asian greens | – | Mar 19–Apr 2 (sow outdoors) | Sep 7–21 (sowing) |
| Arugula | – | Mar 19–Apr 16 (sow outdoors) | Sep 7–Oct 5 (sowing) |
| Mustard greens | – | Mar 19–Apr 9 (sow outdoors) | Sep 7–21 (sowing) |
| Swiss chard | Mar 5–19 | Apr 2–23 (transplant) Apr 2–30 (sow outdoors) | Aug 24–Sep 7 (sowing) |
| Beet | – | Mar 19–Apr 16 (sow outdoors) | Aug 24–Sep 7 (sowing) |
| Carrot | – | Mar 26–Apr 23 (sow outdoors) | Aug 10–24 (sowing) |
| Radish | – | Mar 12–Apr 23 (sow outdoors) | Sep 21–Oct 5 (sowing) |
| Turnip | – | Mar 19–Apr 9 (sow outdoors) | Aug 24–Sep 7 (sowing) |
| Parsnip | – | Mar 26–Apr 16 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Feb 19–Mar 19 (sow outdoors) | Aug 10–24 (sowing) |
| Onion (bulbing) | Jan 22–Feb 5 | Mar 5–19 (transplant) | – |
| Green onion / scallion | – | Mar 5–Apr 2 (sow outdoors) | Aug 24–Sep 7 (sowing) |
| Leek | Jan 22–Feb 5 | Mar 19–Apr 2 (transplant) | – |
| Garlic | – | – | Sep 21–Oct 19 (sowing) |
| Shallot | – | Mar 5–19 (transplant) | Sep 21–Oct 19 (sowing) |
| Potato | – | Mar 19–Apr 2 (transplant) | Jul 13–27 (transplant) |
| Sweet potato | – | May 7–21 (transplant) | – |
| Sweet corn | – | Apr 23–May 7 (sow outdoors) | – |
| Bean, bush (snap) | – | Apr 23–May 7 (sow outdoors) | – |
| Bean, pole | – | Apr 23–May 7 (sow outdoors) | – |
| Lima bean | – | Apr 30–May 14 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | May 7–28 (sow outdoors) | – |
| Cucumber | Mar 19–26 | Apr 23–May 7 (transplant) Apr 23–May 7 (sow outdoors) | – |
| Summer squash / zucchini | Mar 19–26 | Apr 23–May 7 (transplant) Apr 23–May 7 (sow outdoors) | – |
| Winter squash | Mar 19–26 | Apr 23–May 7 (transplant) Apr 23–May 7 (sow outdoors) | – |
| Pumpkin | – | Apr 23–May 7 (sow outdoors) | – |
| Watermelon | Mar 19–26 | Apr 30–May 14 (transplant) Apr 30–May 14 (sow outdoors) | – |
| Cantaloupe / muskmelon | Mar 19–26 | Apr 30–May 14 (transplant) Apr 30–May 14 (sow outdoors) | – |
| Okra | Mar 5–19 | Apr 30–May 14 (transplant) Apr 30–May 14 (sow outdoors) | – |
| Celery | Jan 22–Feb 5 | Apr 23–30 (transplant) | – |
| Basil | Mar 5–19 | Apr 23–May 7 (transplant) Apr 23–May 7 (sow outdoors) | – |
| Cilantro | – | Apr 2–30 (sow outdoors) | Sep 7–21 (sowing) |
| Parsley | Feb 5–19 | Apr 2–16 (transplant) Mar 26–Apr 16 (sow outdoors) | – |
| Dill | – | Apr 16–30 (sow outdoors) | Sep 7–21 (sowing) |
| Sunflower | – | Apr 16–30 (sow outdoors) | – |
| Asparagus (crowns) | – | Mar 19–Apr 2 (transplant) | – |
| Rhubarb (crowns) | – | Mar 19–Apr 2 (transplant) | – |
| Strawberry (plants) | – | Mar 19–Apr 2 (transplant) | Aug 24–Sep 21 (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: Nogales 6 N, AZ (NOAA GHCN-Daily ID USC00025924), elevation 3,461 ft, 3.5 miles from the ZIP's center point. NOAA completeness flag: R (representative, 10+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Tumacacori Nm, AZ | 6 mi | Apr 5 | Nov 10 |
| Nogales Intl AP, AZ | 11 mi | Mar 20 | Nov 17 |
| Santa Rita EXP Range, AZ | 21 mi | Feb 25 | Dec 5 |
The average last-frost dates of these stations span 53 days, a rough guide to local variation. See data sources & methods.
Frost questions for 85648
When is the last frost in 85648?
The average (50% chance) last spring freeze of 32°F for ZIP 85648 is April 16. For a more cautious planting date, use May 4, when only 1 year in 10 still sees a later freeze.
When is the first frost in 85648?
The average first fall freeze is November 2. In 1 year in 10 it comes by October 19.
What hardiness zone is 85648?
ZIP 85648 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 85648 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 85646 Tubac 85621 Nogales 85645 Elephant Head 85624 Patagonia 85601 Arivaca 85622 Green Valley 85614 Green Valley
Other ZIP codes in Santa Cruz County
85611 85621 85624 85637 85640 85646 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.