USDA Hardiness Zone 9b
Frost Dates for 95446 — Guerneville, California
NOAA 1991–2020 normals from Occidental, CA (865 ft), 9 miles south.
Updated
A freeze (32°F) reaches Guerneville in 67% of winters. When it does, the first fall frost comes around December 30 and the last spring frost around January 29; after March 17 the chance of another is under 7%.
- Last spring frost
- January 29
- First fall frost
- December 30
- Winters with a freeze
- 67%
- Hardiness zone
- 9b
50%, in freezing years
50%, in freezing years
32°F or below, 1991–2020
25 to 30°F (-3.9 to -1.1°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 5%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
1 of 20 observed
NOAA normal
Frost risk by date in Guerneville
In the 67% of winters that bring a 32°F night, half of springs at Occidental, CA see their last 32°F night by January 29; only one in ten is past it by December 17, and one in ten still has one after March 17. Counting the winters with no freeze at all, the risk of a 32°F night after March 17 is under 7% and after January 29 33%. The 47 days between the even-odds date and the one-in-ten date is wider than at 96% of the 220 California stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.
In fall the first 32°F night comes by December 30 in half of years, as early as December 1 one year in ten, and holds off past February 27 one year in ten. A hard freeze of 28°F is less common: it came in 10% of winters. The freeze-free season lasts 347 days in a typical year, longer than at 92% of the 219 California stations; it reaches 365 days one year in ten and falls short of 290 one year in ten. On average 3 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 54 days longer, to about March 24, and return around December 8. No night reached 24°F in 1991–2020.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Feb 3 | Feb 23 | Mar 5 | Mar 15 | Mar 24 | Mar 31 | Apr 9 | Apr 16 | Apr 24 |
| 32°F67% of yrs | Dec 17 | Dec 30 | Jan 4 | Jan 15 | Jan 29 | Feb 17 | Feb 27 | Mar 3 | Mar 17 |
| 28°F10% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 20 | Nov 27 | Dec 1 | Dec 5 | Dec 8 | Dec 12 | Dec 17 | Dec 28 | Jan 9 |
| 32°F67% of yrs | Dec 1 | Dec 9 | Dec 16 | Dec 23 | Dec 30 | Jan 4 | Jan 15 | Feb 5 | Feb 27 |
| 28°F10% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Occidental, CA, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 95446 →Compare Guerneville with another place →
Compared with the next station
The nearest other station, Graton, CA, 9 miles southeast of Guerneville and 665 feet lower, has a last frost 50 days later (March 20), a first frost 47 days earlier (November 13), a season 107 days shorter.
When it snows in Guerneville, California
Measurable snow is rare here: only 1 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Occidental, CA, 8.8 miles away, so there is no typical first-snow date to plan around.
Where these figures come from
ZIP 95446 is 9 miles from Occidental, CA, which stands at 865 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 95446 in zone 9b, the band where the coldest night of the year averaged 25 to 30°F (-3.9 to -1.1°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across California →
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.