Frost dates / California / Rohnert Park
Frost dates in Rohnert Park, CA
The station on this page is SANTA ROSA, CA US (USC00047965), 7.5 miles from the city point. Population in the Census 2024 estimate is 44,894.
Zone 9aUSDA average annual extreme minimum 20°F to 25°F, from ZIP 94928 (0.4 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 21 | Earlier date. A last 32°F on or after this day is common. |
| 50% | February 25 | Median. |
| 10% | March 29 | 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 10 | Earlier date. A first 32°F on or before this day is uncommon. |
| 50% | December 1 | Median. |
| 90% | December 24 | 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% | 319 |
| 50% | 279 |
| 90% | 244 |
28°F threshold
| 10% | 50% | 90% | |
|---|---|---|---|
| Last, on or after | February 24 | January 20 | December 22 |
| First, on or before | November 26 | December 16 | January 19 |
| Season at least | 365 days | 335 days | 295 days |
36°F threshold
| 10% | 50% | 90% | |
|---|---|---|---|
| Last, on or after | April 25 | April 3 | March 6 |
| First, on or before | October 31 | November 14 | December 1 |
| Season at least | 256 days | 223 days | 193 days |
Station SANTA ROSA, CA US (USC00047965). Completeness flag R, 22 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 99.4%. Freeze dates are conditional on that threshold occurring. Elevation 50.6 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 Rohnert Park · Zone 9a
Check a crop against this station
Rohnert Park, CA
Zone 9aAverage annual extreme minimum 20°F to 25°F
Outside the median season Growing seasonTicks: 10%, 50%, and 90%
California. Nearest qualified station: SANTA ROSA, CA US (USC00047965), 7.5 miles. Median last 32°F February 25. Median first 32°F December 1. The 50% growing-season length is 279 days.
Open the ZIP page · Crop guides for California
32°F probabilities at this station
| 10% | 50% | 90% | |
|---|---|---|---|
| Last 32°F on or after | March 29 | February 25 | January 21 |
| First 32°F on or before | November 10 | December 1 | December 24 |
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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