Fall in zone 10aPhoto: George Chernilevsky, Public domain, via Wikimedia Commons
Frost dates for ZIP 91761 (Ontario, CA)
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, Ontario Intl AP, CA (1 miles away).
Freezes are uncommon here
NOAA's normals for this station show a 32°F night in about 41% of years (about 2 freezing night(s) a year on average). The dates below describe freeze timing for the station's record; in many years there may be no 32°F freeze at all.
- Average last spring frostJan 450% chance of a 32°F freeze after this date
- Average first fall frostDec 3050% chance of a 32°F freeze by this date
- Growing season (frost-free)year-round in a typical yearmedian, 32°F threshold
- USDA hardiness zone10a30 to 35°F avg. coldest night
Get The Dial for 91761 (Ontario)
Frost and freeze alerts from the NWS forecast for 91761, the spring soil-temperature heads-up for pre-emergent, and a short weekly yard-timing email.
- Freeze alerts
- Soil-temp heads-up
- Weekly yard to-dos
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.
This week in your yard
As of Oct 18, 2026, from your frost dates, zone and soil temperature. Lawn timing · Vegetables · Pruning · Plants
Freezes are uncommon here, so frost-based timing is rough. Local extension calendars for frost-free areas use months.
Soil temperature now
2-inch depth
77°F 55°F or warmer
24-hour average · latest 73°F, as of Oct 18, 1:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Fallbrook 5 NE (47 mi).
4-inch depth
78°F 55°F or warmer
24-hour average · latest 76°F, as of Oct 18, 1:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Fallbrook 5 NE (47 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 91761 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 78°F at 4 inches (estimated soil temperature, not a station reading). Fall pre-emergent (annual bluegrass, winter weeds): not yet. Apply as soil cools toward 70°F (typically September to October).
Fertilizer window
Lawn region: California coastal and valleys. Timing only; always follow the product label.
- Bermudagrass (warm-season): Spring: Several weeks after the lawn is fully green (April–May) (about Feb 19 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).
- Tall fescue (cool-season): Early fall: September (main feeding); Late fall: November, while still green; Late winter: Optional light feeding February–March. Avoid: Feeding after mid-spring and through summer in the transition zone (stress and brown patch).
Plant now
- Kale: fall sowing Sep 23–Oct 21
- Kale: fall transplant Oct 7–Nov 4
- Collards: fall sowing Sep 23–Oct 21
- Collards: fall transplant Oct 7–Nov 4
- Broccoli: fall transplant Sep 23–Oct 21
- Cabbage: fall transplant Sep 23–Oct 21
- Cauliflower: fall transplant Sep 23–Oct 21
- Brussels sprouts: start seeds indoors Oct 12–26
- Carrot: fall sowing Oct 7–21
- Pea (garden, snap, snow): fall sowing Oct 7–21
- Onion (bulbing): start seeds indoors Oct 12–26
- Leek: start seeds indoors Oct 12–26
- Bean, bush (snap): fall sowing Oct 7–21
- Cucumber: fall sowing Oct 7–21
- Summer squash / zucchini: fall sowing Oct 7–21
- Celery: start seeds indoors Oct 12–26
Coming up in the next 3 weeks
- Pepper (sweet and hot): start seeds indoors Oct 26–Nov 9
- Eggplant: start seeds indoors Oct 26–Nov 9
- Lettuce: fall sowing Oct 21–Nov 18
- Lettuce: fall transplant Nov 4–25
- Spinach: fall sowing Nov 4–25
- Broccoli: start seeds indoors Oct 26–Nov 9
- Cabbage: start seeds indoors Oct 26–Nov 9
- Cauliflower: start seeds indoors Oct 26–Nov 9
- Kohlrabi: fall sowing Oct 21–Nov 4
- Bok choy / Asian greens: fall sowing Nov 4–18
- Arugula: fall sowing Nov 4–Dec 2
- Mustard greens: fall sowing Nov 4–18
Prune now
No frost-timed pruning windows are open this week.
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) | Dec 14 (prior Dec) |
| 50% (the "average" last frost) | Jan 4 |
| 10% (cautious: only 1 year in 10 freezes later) | Feb 7 |
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) | Dec 11 |
| 50% (the "average" first frost) | Dec 30 |
| 90% (late: most years have frozen by now) | Feb 1 (next year) |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | Jan 27 | Dec 17 |
| 32°F (freeze) | Jan 4 | Dec 30 |
| 28°F (hard freeze) | n/a | n/a |
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 91761
Dates count from your average last spring frost (Jan 4) and first fall frost (Dec 30). 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 | Nov 9–23 | Jan 11–25 (transplant) | Sep 2–30 (transplant) |
| Pepper (sweet and hot) | Oct 26–Nov 9 | Jan 18–Feb 1 (transplant) | Sep 9–30 (transplant) |
| Eggplant | Oct 26–Nov 9 | Jan 18–Feb 1 (transplant) | Sep 9–30 (transplant) |
| Tomatillo | Nov 9–23 | Jan 11–25 (transplant) | – |
| Lettuce | Nov 9–23 | Dec 14–Jan 4 (transplant) Dec 7–Jan 18 (sow outdoors) | Nov 4–25 (transplant) Oct 21–Nov 18 (sowing) |
| Spinach | – | Nov 23–Dec 14 (sow outdoors) | Nov 4–25 (sowing) |
| Kale | Nov 9–23 | Dec 7–21 (transplant) Dec 7–21 (sow outdoors) | Oct 7–Nov 4 (transplant) Sep 23–Oct 21 (sowing) |
| Collards | Nov 9–23 | Dec 7–Jan 4 (transplant) Dec 7–Jan 4 (sow outdoors) | Oct 7–Nov 4 (transplant) Sep 23–Oct 21 (sowing) |
| Broccoli | Oct 26–Nov 9 | Dec 7–21 (transplant) | Sep 23–Oct 21 (transplant) |
| Cabbage | Oct 26–Nov 9 | Dec 7–21 (transplant) | Sep 23–Oct 21 (transplant) |
| Cauliflower | Oct 26–Nov 9 | Dec 21–Jan 4 (transplant) | Sep 23–Oct 21 (transplant) |
| Brussels sprouts | Oct 12–26 | Dec 7–21 (transplant) | Sep 9–30 (transplant) |
| Kohlrabi | Nov 9–23 | Dec 7–21 (transplant) Dec 7–21 (sow outdoors) | Oct 21–Nov 4 (sowing) |
| Bok choy / Asian greens | – | Dec 7–21 (sow outdoors) | Nov 4–18 (sowing) |
| Arugula | – | Dec 7–Jan 4 (sow outdoors) | Nov 4–Dec 2 (sowing) |
| Mustard greens | – | Dec 7–28 (sow outdoors) | Nov 4–18 (sowing) |
| Swiss chard | Nov 23–Dec 7 | Dec 21–Jan 11 (transplant) Dec 21–Jan 18 (sow outdoors) | Oct 21–Nov 4 (sowing) |
| Beet | – | Dec 7–Jan 4 (sow outdoors) | Oct 21–Nov 4 (sowing) |
| Carrot | – | Dec 14–Jan 11 (sow outdoors) | Oct 7–21 (sowing) |
| Radish | – | Nov 30–Jan 11 (sow outdoors) | Nov 18–Dec 2 (sowing) |
| Turnip | – | Dec 7–28 (sow outdoors) | Oct 21–Nov 4 (sowing) |
| Parsnip | – | Dec 14–Jan 4 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Nov 9–Dec 7 (sow outdoors) | Oct 7–21 (sowing) |
| Onion (bulbing) | Oct 12–26 | Nov 23–Dec 7 (transplant) | – |
| Green onion / scallion | – | Nov 23–Dec 21 (sow outdoors) | Oct 21–Nov 4 (sowing) |
| Leek | Oct 12–26 | Dec 7–21 (transplant) | – |
| Garlic | – | – | Nov 18–Dec 16 (sowing) |
| Shallot | – | Nov 23–Dec 7 (transplant) | Nov 18–Dec 16 (sowing) |
| Potato | – | Dec 7–21 (transplant) | Sep 9–23 (transplant) |
| Sweet potato | – | Jan 25–Feb 8 (transplant) | – |
| Sweet corn | – | Jan 11–25 (sow outdoors) | – |
| Bean, bush (snap) | – | Jan 11–25 (sow outdoors) | Oct 7–21 (sowing) |
| Bean, pole | – | Jan 11–25 (sow outdoors) | – |
| Lima bean | – | Jan 18–Feb 1 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jan 25–Feb 15 (sow outdoors) | – |
| Cucumber | Dec 7–14 | Jan 11–25 (transplant) Jan 11–25 (sow outdoors) | Oct 7–21 (sowing) |
| Summer squash / zucchini | Dec 7–14 | Jan 11–25 (transplant) Jan 11–25 (sow outdoors) | Oct 7–21 (sowing) |
| Winter squash | Dec 7–14 | Jan 11–25 (transplant) Jan 11–25 (sow outdoors) | – |
| Pumpkin | – | Jan 11–25 (sow outdoors) | – |
| Watermelon | Dec 7–14 | Jan 18–Feb 1 (transplant) Jan 18–Feb 1 (sow outdoors) | – |
| Cantaloupe / muskmelon | Dec 7–14 | Jan 18–Feb 1 (transplant) Jan 18–Feb 1 (sow outdoors) | – |
| Okra | Nov 23–Dec 7 | Jan 18–Feb 1 (transplant) Jan 18–Feb 1 (sow outdoors) | – |
| Celery | Oct 12–26 | Jan 11–18 (transplant) | – |
| Basil | Nov 23–Dec 7 | Jan 11–25 (transplant) Jan 11–25 (sow outdoors) | – |
| Cilantro | – | Dec 21–Jan 18 (sow outdoors) | Nov 4–18 (sowing) |
| Parsley | Oct 26–Nov 9 | Dec 21–Jan 4 (transplant) Dec 14–Jan 4 (sow outdoors) | – |
| Dill | – | Jan 4–18 (sow outdoors) | Nov 4–18 (sowing) |
| Sunflower | – | Jan 4–18 (sow outdoors) | – |
| Asparagus (crowns) | – | Dec 7–21 (transplant) | – |
| Rhubarb (crowns) | – | Dec 7–21 (transplant) | – |
| Strawberry (plants) | – | Dec 7–21 (transplant) | Oct 21–Nov 18 (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: Ontario Intl AP, CA (NOAA GHCN-Daily ID USW00003102), elevation 949 ft, 1.5 miles from the ZIP's center point. NOAA completeness flag: R (representative, 10+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Chino AP, CA | 5 mi | Jan 17 | Dec 19 |
| Pomona/fairplex, CA | 11 mi | Jan 8 | Dec 28 |
| Riverside Muni AP, CA | 11 mi | Jan 9 | Dec 30 |
The average last-frost dates of these stations span 13 days, a rough guide to local variation. See data sources & methods.
Frost questions for 91761
When is the last frost in 91761?
The average (50% chance) last spring freeze of 32°F for ZIP 91761 is January 4. For a more cautious planting date, use February 7, when only 1 year in 10 still sees a later freeze.
When is the first frost in 91761?
The average first fall freeze is December 30. In 1 year in 10 it comes by December 11.
What hardiness zone is 91761?
ZIP 91761 is in USDA zone 10a (30 to 35°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 91761 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
91764 Ontario 91752 Jurupa Valley 91730 Rancho Cucamonga 91762 Ontario 91710 Chino 91786 Upland 91708 Chino 91763 Montclair
Other ZIP codes in San Bernardino County
91701 91708 91709 91710 91730 91737 91739 91762 91763 91764 91784 91786 92242 92252 92256 92267 92268 92277 92278 92280 92284 92285 92301 92304 All San Bernardino County frost dates · California frost dates
Never miss a frost: get The Dial
Weekly yard timing, plus frost and soil-temperature alerts for your ZIP code.
- Freeze alerts
- Soil-temp heads-up
- Weekly yard to-dos
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.