Frost dates / California / Walnut Creek
Frost dates in Walnut Creek, CA
The station on this page is CONCORD WWTP, CA US (USC00041967), 5.8 miles from the city point. Population in the Census 2024 estimate is 70,817.
Zone 9bUSDA average annual extreme minimum 25°F to 30°F, from ZIP 94596 (1 miles from the city point used on this page).
Outside the median season Growing seasonTicks: 10%, 50%, and 90%
Last 32°F in spring
NCEI’s probability is the chance the last spring minimum of 32°F or lower occurs on or after the date.
| Probability | Date | How to read it |
|---|---|---|
| 90% | December 19 | Earlier date. A last 32°F on or after this day is common. |
| 50% | January 7 | Median. |
| 10% | February 1 | Later date. A last 32°F on or after this day is uncommon. |
First 32°F in fall
NCEI’s probability is the chance the first autumn minimum of 32°F or lower occurs on or before the date.
| Probability | Date | How to read it |
|---|---|---|
| 10% | December 1 | Earlier date. A first 32°F on or before this day is uncommon. |
| 50% | December 19 | Median. |
| 90% | January 12 | Later date. A first 32°F on or before this day is common. |
32°F growing-season length
Days between the last spring 32°F and the first autumn 32°F. The figure is a length the season meets or exceeds at that probability, from NCEI, not a subtraction done on this site.
| Probability the season is at least this long | Days |
|---|---|
| 10% | 365 |
| 50% | 346 |
| 90% | 315 |
28°F threshold
| 10% | 50% | 90% | |
|---|---|---|---|
| Last, on or after | January 20 | December 31 | December 14 |
| First, on or before | December 10 | December 29 | January 14 |
| Season at least | 365 days | 365 days | 350 days |
36°F threshold
| 10% | 50% | 90% | |
|---|---|---|---|
| Last, on or after | March 6 | February 9 | January 6 |
| First, on or before | November 15 | December 2 | December 24 |
| Season at least | 333 days | 297 days | 264 days |
Station CONCORD WWTP, CA US (USC00041967). Completeness flag R, 21 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 79.9%. Freeze dates are conditional on that threshold occurring. Elevation 12.2 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.
Planting calendar for Walnut Creek · Zone 9b
Check a crop against this station
Walnut Creek, CA
Zone 9bAverage annual extreme minimum 25°F to 30°F
Outside the median season Growing seasonTicks: 10%, 50%, and 90%
California. Nearest qualified station: CONCORD WWTP, CA US (USC00041967), 5.8 miles. Median last 32°F January 7. Median first 32°F December 19. The 50% growing-season length is 346 days.
Open the ZIP page · Crop guides for California
32°F probabilities at this station
| 10% | 50% | 90% | |
|---|---|---|---|
| Last 32°F on or after | February 1 | January 7 | December 19 |
| First 32°F on or before | December 1 | December 19 | January 12 |
Column order matches the NCEI file: for the last freeze, 10% is the later date and 90% is the earlier date. How to read the probabilities.
Planting calendar
Windows below are from UC ANR, UC Master Gardener Program, Time of planting, retrieved 2026-10-10. North and North Coast = Monterey County north; South Coast = San Luis Obispo County south; Interior Valleys = Sacramento, San Joaquin, and similar valleys; Desert Valleys = Imperial and Coachella Valleys. Source line on the page: California Master Gardener Handbook, Table 13.2, Adapted from Vegetable Gardening Illustrated 1994.
Date checks use your device’s calendar and appear after the page loads.