Frost dates · USDA zone 9b
Frost dates for Walnut Creek, CA
Walnut Creek, CA sees its last 32 °F night of spring around March 8 and its first of fall around December 22 — a 282-day freeze-free season in a typical year.
Pick a sauce; the Plan Builder runs this station's dates and hands back the calendar, plant count and gear list.
Freeze odds, by date
| Odds | Last spring freeze after | First fall freeze before |
|---|---|---|
| 9 years in 10 | Jan 12 | Feb 11 (next year) |
| Median — 1 year in 2 | Mar 8 | Dec 22 |
| 1 year in 10 | Apr 15 | Nov 23 |
The top row is the risky edge: in 9 years of 10 a spring freeze still comes after it, so tender transplants set out then need cover. The bottom row is the cautious date — only 1 year in 10 freezes after it — and the one to plan uncovered tender transplants against. Freeze-free season: 282 days median, at least 238 in 9 years of 10, at least 343 days in 1 year of 10. NOAA ranks season length year by year, so it is not the gap between two rows above. A hard freeze (28 °F) has a median last date of Feb 8 and first of Jan 16 (next year).
Walnut Creek planting calendar, 2027
Every row runs from the median last frost (Mar 8) and median first frost (Dec 22) above, using each cultivar's days to maturity. Same engine as the Plan Builder.
| Crop | Start indoors | Transplant / plant | First harvest | Days |
|---|---|---|---|---|
| Hardneck GarlicSiberian (porcelain hardneck) | — | Oct 15prior fall | Jun 12 | 240 from sow |
| Spanish OnionYellow Sweet Spanish (long-day) | Dec 14 | Feb 8 | May 29 | 110 from transplant |
| Mustard greensGarnet Giant (Brassica juncea) | Direct sow | Mar 8 | Apr 7 | 30 from sow |
| CilantroSlow Bolt (Coriandrum sativum) | Feb 22 | Feb 22 | Apr 8 | 45 from sow |
| Genovese BasilGenovese | Feb 8 | Mar 22 | May 21 | 60 from transplant |
| CayenneLong Slim Cayenne (Capsicum annuum) | Jan 11 | Mar 15 | May 29 | 75 from transplant |
| HabaneroOrange Habanero (Capsicum chinense) | Dec 28 | Mar 22 | Jun 25 | 95 from transplant |
| JalapeñoEarly Jalapeño (Capsicum annuum) | Jan 11 | Mar 15 | May 29 | 75 from transplant |
| Marconi Red PepperMarconi Red (Capsicum annuum) | Jan 11 | Mar 15 | Jun 3 | 80 from transplant |
| SerranoSerrano Tampiqueño (Capsicum annuum) | Jan 11 | Mar 15 | Jun 3 | 80 from transplant |
| Nantes CarrotScarlet Nantes | Feb 22 | Feb 22 | May 3 | 70 from sow |
| TomatilloToma Verde | Jan 25 | Mar 15 | May 24 | 70 from transplant |
| Roma TomatoRoma VF (determinate paste) | Jan 25 | Mar 15 | May 29 | 75 from transplant |
| San Marzano TomatoSan Marzano (indeterminate paste) | Jan 25 | Mar 15 | Jun 3 | 80 from transplant |
Tight means first harvest lands within two weeks of the median first fall frost: start that crop indoors on time or cover it in fall.
What sauce can Walnut Creek grow?
Each sauce, scheduled for a Walnut Creek container garden: when the first seeds go in and when enough fruit has ripened for one batch.
Walnut Creek frost questions
When is the last frost in Walnut Creek, CA?
The median last 32 °F freeze at MT DIABLO JUNCTION, CA is March 8: half of years see a later one. One year in ten, a freeze still comes after April 15; nine years in ten, it comes after January 12. Source: NOAA NCEI 1991–2020 U.S. Climate Normals.
When is the first frost in Walnut Creek, CA?
The median first 32 °F freeze of fall is December 22. One year in ten it arrives before November 23; nine years in ten, before February 11 (next year).
How long is the growing season in Walnut Creek, CA?
282 days between the last spring and first fall 32 °F freeze in a median year. Nine years in ten the season runs at least 238 days; one year in ten, at least 343 days.
What growing zone is Walnut Creek, CA?
USDA hardiness zone 9b, per the 2023 USDA Plant Hardiness Zone Map for ZIP 94596. A zone describes the coldest winter night, not when frost ends, so it is the wrong number for a planting calendar — the frost dates on this page are the right one.
When should I plant tomatoes in Walnut Creek, CA?
Start Roma VF (determinate paste) seeds indoors around Jan 25 and transplant around Mar 15, 1 week after the median last frost. To cut the freeze risk to one year in ten, wait for Apr 15. First ripe fruit lands around May 29.
When should I plant peppers in Walnut Creek, CA?
Sow jalapeño indoors on a heat mat around Jan 11; transplant no earlier than Mar 15, and wait past it until nights hold above 50 °F — that can run weeks later. First green pods around May 29.
Nearby in California
- Concordlast frost Jan 9
- Danvillelast frost Mar 8
- Pittsburglast frost Jan 9
- San Ramonlast frost Feb 15
- Oaklandfrost rare
- Antiochlast frost Jan 12
All California frost dates → · How frost-date math drives a sowing calendar →