Frost dates / California / Vallejo
Frost dates in Vallejo, CA
The station on this page is NAPA CO AP, CA US (USW00093227), 7.2 miles from the city point. Population in the Census 2024 estimate is 123,475.
Zone 9bUSDA average annual extreme minimum 25°F to 30°F, from ZIP 94590 (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% | January 26 | Earlier date. A last 32°F on or after this day is common. |
| 50% | March 5 | Median. |
| 10% | April 16 | 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% | November 3 | Earlier date. A first 32°F on or before this day is uncommon. |
| 50% | November 21 | Median. |
| 90% | December 13 | 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% | 305 |
| 50% | 256 |
| 90% | 212 |
28°F threshold
| 10% | 50% | 90% | |
|---|---|---|---|
| Last, on or after | February 28 | January 23 | December 20 |
| First, on or before | November 16 | December 5 | January 11 |
| Season at least | 361 days | 323 days | 279 days |
36°F threshold
| 10% | 50% | 90% | |
|---|---|---|---|
| Last, on or after | May 9 | April 17 | March 17 |
| First, on or before | October 16 | November 4 | November 22 |
| Season at least | 230 days | 199 days | 171 days |
Station NAPA CO AP, CA US (USW00093227). 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 99.7%. Freeze dates are conditional on that threshold occurring. Elevation 4.3 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 Vallejo · Zone 9b
Check a crop against this station
Vallejo, 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: NAPA CO AP, CA US (USW00093227), 7.2 miles. Median last 32°F March 5. Median first 32°F November 21. The 50% growing-season length is 256 days.
Open the ZIP page · Crop guides for California
32°F probabilities at this station
| 10% | 50% | 90% | |
|---|---|---|---|
| Last 32°F on or after | April 16 | March 5 | January 26 |
| First 32°F on or before | November 3 | November 21 | December 13 |
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.
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