USDA Hardiness Zone 9b
Frost Dates for 95521 — Arcata, California
NOAA 1991–2020 normals from Eureka WFO Woodley Island, CA (20 ft), 6 miles southwest.
Updated
In Arcata, the last spring frost (32°F) is around February 22 in half of years and has passed by March 23 in nine years out of ten. The first fall frost comes around December 7, as early as November 15 one year in ten, leaving a typical freeze-free season of 293 days (NOAA, Eureka WFO Woodley Island, CA).
- Last spring frost
- February 22
- First fall frost
- December 7
- Growing season
- 293 days
- Hardiness zone
- 9b
50% probability
50% probability
freeze-free, 50%
25 to 30°F (-3.9 to -1.1°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 13%
- Snow per year
- 0"
median, 1991–2020
median, 1991–2020
4 of 30 observed
NOAA normal
Frost risk by date in Arcata
Half of springs at Eureka WFO Woodley Island, CA see their last 32°F night by February 22; only one in ten is past it by December 31, and one in ten still has one after March 23. Planting tender crops after March 4 leaves a 30% risk of a frost on them, after March 14 20%, and after March 23 10%. The 29 days between the even-odds date and the one-in-ten date is narrower than at 52% 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 7 in half of years, as early as November 15 one year in ten, and holds off past January 11 one year in ten. A hard freeze of 28°F is less common: it came in 48% of winters. The freeze-free season lasts 293 days in a typical year, longer than at 60% of the 219 California stations; it reaches 343 days one year in ten and falls short of 251 one year in ten. On average 8 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 38 days longer, to about April 1, and return around November 12. A 24°F night is unusual: 5% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 1 | Mar 13 | Mar 21 | Mar 28 | Apr 1 | Apr 4 | Apr 9 | Apr 14 | Apr 22 |
| 32°F97% of yrs | Dec 31 | Jan 18 | Feb 2 | Feb 13 | Feb 22 | Feb 28 | Mar 4 | Mar 14 | Mar 23 |
| 28°F48% of yrs | too rare for a date | ||||||||
| 24°F5% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 25 | Nov 1 | Nov 4 | Nov 8 | Nov 12 | Nov 16 | Nov 22 | Nov 27 | Dec 4 |
| 32°F97% of yrs | Nov 15 | Nov 21 | Nov 28 | Dec 2 | Dec 7 | Dec 11 | Dec 17 | Dec 27 | Jan 11 |
| 28°F48% of yrs | too rare for a date | ||||||||
| 24°F5% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Eureka WFO Woodley Island, 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 95521 →Compare Arcata with another place →
Weather by month in Arcata
August is the warmest month at Eureka WFO Woodley Island, CA, averaging 64°F by day and 53°F at night; December is the coldest at 55°F and 40°F. From April to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 53% of years and March still brings one in 33% of years.
Warmth for growing adds up to 1,415 growing degree days a year (base 50°F), fewer than at 97% of the 283 California stations. 32% of them (456) have built up by the end of June, and August adds the most, 264. Precipitation totals 40.5 inches a year, most in December (8.1") and least in July (0.2"); May to September bring 9% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 55 | 41 | 6.7 | 60% | 2 | 34 |
| Feb | 55 | 41 | 5.6 | 53% | 1 | 32 |
| Mar | 56 | 42 | 5.8 | 33% | 1 | 39 |
| Apr | 57 | 44 | 3.6 | 3% | <1 | 53 |
| May | 60 | 48 | 1.7 | 0% | 0 | 118 |
| Jun | 62 | 50 | 0.7 | 0% | 0 | 180 |
| Jul | 63 | 52 | 0.2 | 0% | 0 | 240 |
| Aug | 64 | 53 | 0.2 | 0% | 0 | 264 |
| Sep | 64 | 51 | 0.7 | 0% | 0 | 216 |
| Oct | 62 | 47 | 2.3 | 0% | 0 | 142 |
| Nov | 58 | 43 | 4.9 | 33% | 1 | 65 |
| Dec | 55 | 40 | 8.1 | 71% | 3 | 31 |
Monthly normals 1991–2020 at Eureka WFO Woodley Island, CA (20 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Arcata Eureka Airport, CA, 8 miles north of Arcata and 180 feet higher, has a last frost 14 days later (March 8), a first frost 7 days earlier (November 30), a season 31 days shorter.
When it snows in Arcata, California
Measurable snow is rare here: only 4 of 30 winters from 1991 to 2020 recorded 0.1 inch or more at Eureka WFO Woodley Island, CA, 6 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 95521
| When | What to do |
|---|---|
| December 14 – December 28 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| December 28 – January 11 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| January 25 – February 8 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| February 22 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 14 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 23 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 7 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 95521 is 6 miles from Eureka WFO Woodley Island, CA, which stands at 20 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 95503 (Eureka). The 2023 USDA Plant Hardiness Zone Map lists ZIP 95521 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.