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Will it freeze in St. Helena in the next 7 nights?
No overnight lows at or below 32°F are forecast in St. Helena during the next 7 nights in the available NWS frost forecast.
Tonight: forecast low 44°F. Above 36°F.
NWS forecast period: Thu, Nov 5, 6:00 PM PST to Fri, Nov 6, 6:00 AM PST.
No nights at or below 36°F in the National Weather Service forecast for the next 7 nights.
- Tonight 44°F Above 36°F · Mostly Clear
- Fri, Nov 6 43°F Above 36°F · Mostly Clear
- Sat, Nov 7 43°F Above 36°F · Partly Cloudy then Patchy Fog
- Sun, Nov 8 45°F Above 36°F · Partly Cloudy then Areas Of Fog
- Mon, Nov 9 44°F Above 36°F · Partly Cloudy then Patchy Fog
- Tue, Nov 10 46°F Above 36°F · Partly Cloudy then Areas Of Fog
- Wed, Nov 11 45°F Above 36°F · Chance Light Rain
Overnight lows from the National Weather Service forecast for this location. This covers the available forecast window, not the first freeze of the whole season. Frost can form above 32°F on clear, calm nights.
Frost and freeze probabilities
Freeze dates shift from year to year. Spring percentages describe the chance of a freeze after the stated date; fall percentages describe the chance of a freeze by that date. The 10% spring date is the cautious one: a later freeze happens about 1 year in 10.
These dates describe historical probabilities, not this year’s forecast or the earliest and latest possible freezes. Different weather stations or probability thresholds can produce different published dates for the same city.
Average first hard freeze in St. Helena
The median first fall hard-freeze date (28°F) is December 17, from NOAA’s 1991–2020 Climate Normals at Saint Helena. This is the 50% probability date, not a forecast for this year.
| Temperature | Last spring date 90% · 50% · 10% chance of a later freeze | First fall date 10% · 50% · 90% chance of an earlier freeze | Season |
|---|---|---|---|
| 36°F frost possible | Feb 14 · Mar 19 · Apr 17 | Oct 31 · Nov 18 · Dec 5 | 243 days |
| 32°F freeze | Dec 28 · Feb 3 · Mar 13 | Nov 14 · Dec 4 · Jan 1 | 306 days |
| 28°F hard freeze | Dec 11 · Jan 5 · Feb 9 | Nov 27 · Dec 17 · Jan 18 | 349 days |
Average high temperature by month
1991–2020 normals at Saint Helena
Average low temperature by month
Months with lows near or below freezing carry frost risk
Where these frost dates come from
The frost dates for St. Helena, CA come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Saint Helena (station USC00047643, elevation 225 ft), 0.4 mi from St. Helena. Local conditions (valleys, hilltops, distance to water, city heat) can shift frost dates by days or weeks. The hardiness zone is from the 2023 USDA Plant Hardiness Zone Map (USDA ARS and Oregon State University PRISM). See our methodology.
Frost dates near St. Helena
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Santa Rosa, CA | 14 mi | Feb 25 | Dec 1 |
| Sonoma, CA | 16 mi | Mar 2 | Nov 27 |
| Rohnert Park, CA | 17 mi | Feb 25 | Dec 1 |
| Napa, CA | 17 mi | Feb 12 | Dec 4 |
| Cotati, CA | 18 mi | Feb 28 | Nov 25 |
| Windsor, CA | 19 mi | Mar 2 | Nov 20 |
| Petaluma, CA | 21 mi | Feb 28 | Nov 25 |
| Sebastopol, CA | 21 mi | Mar 20 | Nov 13 |
| Healdsburg, CA | 23 mi | Feb 15 | Dec 2 |
| American Canyon, CA | 25 mi | Mar 5 | Nov 21 |
Frequently asked questions
When is the last frost in St. Helena?
On average, the last spring frost (32°F) in St. Helena is around February 3. In about 1 year in 10 it comes after March 13, and in 9 years in 10 it comes after December 28.
When is the first frost in St. Helena?
The first fall frost (32°F) usually arrives around December 4. There’s a 10% chance of a freeze by November 14 and a 90% chance by January 1.
Can it frost in St. Helena after the last frost date?
Yes. Frost can form on clear, calm nights even when the air stays above 32°F. Temperatures of 36°F or lower, cold enough for frost on exposed plants, have a 50% chance of occurring after March 19.
What growing zone is St. Helena?
St. Helena is in USDA Plant Hardiness Zone 9b (average annual extreme minimum temperature 25 to 30°F), based on the 2023 USDA map for ZIP code 94576. See growing zones in California.
More: all California frost dates · California growing zones · frost vs. freeze