Fall in zone 10aPhoto: George Chernilevsky, Public domain, via Wikimedia Commons
Frost dates for ZIP 92521 (Riverside, 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, Riverside Citrus EXP, CA (2 miles away).
Freezes are uncommon here
NOAA's normals for this station show a 32°F night in about 45% 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 1050% chance of a 32°F freeze after this date
- Average first fall frostJan 2 (next year)50% 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
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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
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 (37 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 (37 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 92521 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 25 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 26–Oct 24
- Kale: fall transplant Oct 10–Nov 7
- Collards: fall sowing Sep 26–Oct 24
- Collards: fall transplant Oct 10–Nov 7
- Broccoli: fall transplant Sep 26–Oct 24
- Cabbage: fall transplant Sep 26–Oct 24
- Cauliflower: fall transplant Sep 26–Oct 24
- Brussels sprouts: start seeds indoors Oct 18–Nov 1
- Carrot: fall sowing Oct 10–24
- Pea (garden, snap, snow): fall sowing Oct 10–24
- Onion (bulbing): start seeds indoors Oct 18–Nov 1
- Leek: start seeds indoors Oct 18–Nov 1
- Bean, bush (snap): fall sowing Oct 10–24
- Cucumber: fall sowing Oct 10–24
- Summer squash / zucchini: fall sowing Oct 10–24
- Celery: start seeds indoors Oct 18–Nov 1
Coming up in the next 3 weeks
- Pepper (sweet and hot): start seeds indoors Nov 1–15
- Eggplant: start seeds indoors Nov 1–15
- Lettuce: fall sowing Oct 24–Nov 21
- Lettuce: fall transplant Nov 7–28
- Spinach: fall sowing Nov 7–28
- Broccoli: start seeds indoors Nov 1–15
- Cabbage: start seeds indoors Nov 1–15
- Cauliflower: start seeds indoors Nov 1–15
- Kohlrabi: fall sowing Oct 24–Nov 7
- Bok choy / Asian greens: fall sowing Nov 7–21
- Arugula: fall sowing Nov 7–Dec 5
- Mustard greens: fall sowing Nov 7–21
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 20 (prior Dec) |
| 50% (the "average" last frost) | Jan 10 |
| 10% (cautious: only 1 year in 10 freezes later) | Feb 17 |
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) | Jan 2 (next year) |
| 90% (late: most years have frozen by now) | Feb 7 (next year) |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | Feb 11 | Dec 13 |
| 32°F (freeze) | Jan 10 | Jan 2 (next year) |
| 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 92521
Dates count from your average last spring frost (Jan 10) and first fall frost (Jan 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 | Nov 15–29 | Jan 17–31 (transplant) | Sep 5–Oct 3 (transplant) |
| Pepper (sweet and hot) | Nov 1–15 | Jan 24–Feb 7 (transplant) | Sep 12–Oct 3 (transplant) |
| Eggplant | Nov 1–15 | Jan 24–Feb 7 (transplant) | Sep 12–Oct 3 (transplant) |
| Tomatillo | Nov 15–29 | Jan 17–31 (transplant) | – |
| Lettuce | Nov 15–29 | Dec 20–Jan 10 (transplant) Dec 13–Jan 24 (sow outdoors) | Nov 7–28 (transplant) Oct 24–Nov 21 (sowing) |
| Spinach | – | Nov 29–Dec 20 (sow outdoors) | Nov 7–28 (sowing) |
| Kale | Nov 15–29 | Dec 13–27 (transplant) Dec 13–27 (sow outdoors) | Oct 10–Nov 7 (transplant) Sep 26–Oct 24 (sowing) |
| Collards | Nov 15–29 | Dec 13–Jan 10 (transplant) Dec 13–Jan 10 (sow outdoors) | Oct 10–Nov 7 (transplant) Sep 26–Oct 24 (sowing) |
| Broccoli | Nov 1–15 | Dec 13–27 (transplant) | Sep 26–Oct 24 (transplant) |
| Cabbage | Nov 1–15 | Dec 13–27 (transplant) | Sep 26–Oct 24 (transplant) |
| Cauliflower | Nov 1–15 | Dec 27–Jan 10 (transplant) | Sep 26–Oct 24 (transplant) |
| Brussels sprouts | Oct 18–Nov 1 | Dec 13–27 (transplant) | Sep 12–Oct 3 (transplant) |
| Kohlrabi | Nov 15–29 | Dec 13–27 (transplant) Dec 13–27 (sow outdoors) | Oct 24–Nov 7 (sowing) |
| Bok choy / Asian greens | – | Dec 13–27 (sow outdoors) | Nov 7–21 (sowing) |
| Arugula | – | Dec 13–Jan 10 (sow outdoors) | Nov 7–Dec 5 (sowing) |
| Mustard greens | – | Dec 13–Jan 3 (sow outdoors) | Nov 7–21 (sowing) |
| Swiss chard | Nov 29–Dec 13 | Dec 27–Jan 17 (transplant) Dec 27–Jan 24 (sow outdoors) | Oct 24–Nov 7 (sowing) |
| Beet | – | Dec 13–Jan 10 (sow outdoors) | Oct 24–Nov 7 (sowing) |
| Carrot | – | Dec 20–Jan 17 (sow outdoors) | Oct 10–24 (sowing) |
| Radish | – | Dec 6–Jan 17 (sow outdoors) | Nov 21–Dec 5 (sowing) |
| Turnip | – | Dec 13–Jan 3 (sow outdoors) | Oct 24–Nov 7 (sowing) |
| Parsnip | – | Dec 20–Jan 10 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Nov 15–Dec 13 (sow outdoors) | Oct 10–24 (sowing) |
| Onion (bulbing) | Oct 18–Nov 1 | Nov 29–Dec 13 (transplant) | – |
| Green onion / scallion | – | Nov 29–Dec 27 (sow outdoors) | Oct 24–Nov 7 (sowing) |
| Leek | Oct 18–Nov 1 | Dec 13–27 (transplant) | – |
| Garlic | – | – | Nov 21–Dec 19 (sowing) |
| Shallot | – | Nov 29–Dec 13 (transplant) | Nov 21–Dec 19 (sowing) |
| Potato | – | Dec 13–27 (transplant) | Sep 12–26 (transplant) |
| Sweet potato | – | Jan 31–Feb 14 (transplant) | – |
| Sweet corn | – | Jan 17–31 (sow outdoors) | – |
| Bean, bush (snap) | – | Jan 17–31 (sow outdoors) | Oct 10–24 (sowing) |
| Bean, pole | – | Jan 17–31 (sow outdoors) | – |
| Lima bean | – | Jan 24–Feb 7 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jan 31–Feb 21 (sow outdoors) | – |
| Cucumber | Dec 13–20 | Jan 17–31 (transplant) Jan 17–31 (sow outdoors) | Oct 10–24 (sowing) |
| Summer squash / zucchini | Dec 13–20 | Jan 17–31 (transplant) Jan 17–31 (sow outdoors) | Oct 10–24 (sowing) |
| Winter squash | Dec 13–20 | Jan 17–31 (transplant) Jan 17–31 (sow outdoors) | – |
| Pumpkin | – | Jan 17–31 (sow outdoors) | – |
| Watermelon | Dec 13–20 | Jan 24–Feb 7 (transplant) Jan 24–Feb 7 (sow outdoors) | – |
| Cantaloupe / muskmelon | Dec 13–20 | Jan 24–Feb 7 (transplant) Jan 24–Feb 7 (sow outdoors) | – |
| Okra | Nov 29–Dec 13 | Jan 24–Feb 7 (transplant) Jan 24–Feb 7 (sow outdoors) | – |
| Celery | Oct 18–Nov 1 | Jan 17–24 (transplant) | – |
| Basil | Nov 29–Dec 13 | Jan 17–31 (transplant) Jan 17–31 (sow outdoors) | – |
| Cilantro | – | Dec 27–Jan 24 (sow outdoors) | Nov 7–21 (sowing) |
| Parsley | Nov 1–15 | Dec 27–Jan 10 (transplant) Dec 20–Jan 10 (sow outdoors) | – |
| Dill | – | Jan 10–24 (sow outdoors) | Nov 7–21 (sowing) |
| Sunflower | – | Jan 10–24 (sow outdoors) | – |
| Asparagus (crowns) | – | Dec 13–27 (transplant) | – |
| Rhubarb (crowns) | – | Dec 13–27 (transplant) | – |
| Strawberry (plants) | – | Dec 13–27 (transplant) | Oct 24–Nov 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: Riverside Citrus EXP, CA (NOAA GHCN-Daily ID USC00047473), elevation 986 ft, 2.0 miles from the ZIP's center point. NOAA completeness flag: R (representative, 10+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Riverside Fire STN 3, CA | 4 mi | Jan 9 | Dec 25 |
| Riverside Muni AP, CA | 7 mi | Jan 9 | Dec 30 |
| Redlands, CA | 9 mi | Jan 27 | Dec 19 |
The average last-frost dates of these stations span 18 days, a rough guide to local variation. See data sources & methods.
Frost questions for 92521
When is the last frost in 92521?
The average (50% chance) last spring freeze of 32°F for ZIP 92521 is January 10. For a more cautious planting date, use February 17, when only 1 year in 10 still sees a later freeze.
When is the first frost in 92521?
The average first fall freeze is January 2 (next year). In 1 year in 10 it comes by December 11.
What hardiness zone is 92521?
ZIP 92521 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 92521 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
92507 Riverside 92506 Riverside 92501 Riverside 92557 Moreno Valley 92313 Grand Terrace 92324 Colton 92508 Riverside 92553 Moreno Valley
Other ZIP codes in Riverside County
91752 92201 92203 92210 92211 92220 92223 92225 92230 92234 92236 92239 92240 92241 92253 92254 92258 92260 92262 92264 92270 92274 92276 92282 All Riverside County frost dates · California frost dates
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- 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.