USDA Hardiness Zone 9a
Frost Dates for 97380 — Siletz, Oregon
NOAA 1991–2020 normals from Newport 3N, OR (220 ft), 8 miles southwest.
Updated
In Siletz, the last spring frost (32°F) is around March 12 in half of years and has passed by April 16 in nine years out of ten. The first fall frost comes around December 10, as early as November 7 one year in ten, leaving a typical freeze-free season of 271 days (NOAA, Newport 3N, OR).
- Last spring frost
- March 12
- First fall frost
- December 10
- Growing season
- 271 days
- Hardiness zone
- 9a
50% probability
50% probability
freeze-free, 50%
20 to 25°F (-6.7 to -3.9°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 15%
- Snow per year
- 0.1"
median, 1991–2020
median, 1991–2020
3 of 20 observed
NOAA normal
Frost risk by date in Siletz
Half of springs at Newport 3N, OR see their last 32°F night by March 12; only one in ten is past it by January 24, and one in ten still has one after April 16. Planting tender crops after March 28 leaves a 30% risk of a frost on them, after April 4 20%, and after April 16 10%. The 35 days between the even-odds date and the one-in-ten date is wider than at 96% of the 103 Oregon 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 10 in half of years, as early as November 7 one year in ten, and holds off past February 8 one year in ten. A hard freeze of 28°F follows 18 days later, around December 28; in spring the one-in-ten date for 28°F is March 5, 42 days before the 32°F one. The freeze-free season lasts 271 days in a typical year, longer than at 93% of the 103 Oregon stations; it reaches 327 days one year in ten and falls short of 226 one year in ten. On average 15 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 39 days longer, to about April 20, and return around November 9. A 24°F night is unusual: 28% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 25 | Apr 3 | Apr 10 | Apr 15 | Apr 20 | Apr 26 | Apr 29 | May 2 | May 8 |
| 32°F98% of yrs | Jan 24 | Feb 13 | Feb 23 | Mar 1 | Mar 12 | Mar 21 | Mar 28 | Apr 4 | Apr 16 |
| 28°F67% of yrs | Dec 7 | Dec 24 | Jan 6 | Jan 17 | Jan 28 | Feb 6 | Feb 18 | Feb 25 | Mar 5 |
| 24°F28% of yrs | too rare for a date | ||||||||
| 20°F5% of yrs | too rare for a date | ||||||||
| 16°F1% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 13 | Oct 23 | Oct 30 | Nov 3 | Nov 9 | Nov 14 | Nov 21 | Nov 29 | Dec 9 |
| 32°F98% of yrs | Nov 7 | Nov 17 | Nov 26 | Dec 3 | Dec 10 | Dec 21 | Jan 1 | Jan 14 | Feb 8 |
| 28°F67% of yrs | Nov 24 | Dec 1 | Dec 9 | Dec 17 | Dec 28 | Jan 4 | Jan 18 | Feb 1 | Feb 20 |
| 24°F28% of yrs | too rare for a date | ||||||||
| 20°F5% of yrs | too rare for a date | ||||||||
| 16°F1% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Newport 3N, OR, 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 97380 →Compare Siletz with another place →
Weather by month in Siletz
August is the warmest month at Newport 3N, OR, averaging 66°F by day and 51°F at night; February is the coldest at 54°F and 41°F. From May to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 64% of years and March still brings one in 49% of years and April still brings one in 23% of years.
Warmth for growing adds up to 1,424 growing degree days a year (base 50°F), fewer than at 92% of the 103 Oregon stations. 29% of them (410) have built up by the end of June, and August adds the most, 270.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 55 | 42 | 56% | 4 | 48 |
| Feb | 54 | 41 | 64% | 3 | 35 |
| Mar | 54 | 41 | 49% | 3 | 36 |
| Apr | 56 | 42 | 23% | <1 | 34 |
| May | 59 | 46 | 0% | 0 | 92 |
| Jun | 62 | 49 | 0% | 0 | 165 |
| Jul | 65 | 51 | 0% | 0 | 253 |
| Aug | 66 | 51 | 0% | 0 | 270 |
| Sep | 66 | 49 | 0% | 0 | 221 |
| Oct | 62 | 47 | 5% | <1 | 154 |
| Nov | 56 | 45 | 31% | 1 | 73 |
| Dec | 53 | 42 | 53% | 3 | 43 |
Monthly normals 1991–2020 at Newport 3N, OR (220 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, Newport, OR, 10 miles southwest of Siletz, has a last frost 9 days later (March 21), a first frost 13 days earlier (November 27), a season 19 days shorter.
When it snows in Siletz, Oregon
Measurable snow is rare here: only 3 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Newport, OR, 9.7 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 97380
| When | What to do |
|---|---|
| January 1 – January 15 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| January 15 – January 29 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| February 12 – February 26 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| March 12 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 17 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 26 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 10 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 97380 is 8 miles from Newport 3N, OR, which stands at 220 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 97341 (Depoe Bay). The 2023 USDA Plant Hardiness Zone Map lists ZIP 97380 in zone 9a, the band where the coldest night of the year averaged 20 to 25°F (-6.7 to -3.9°C) over 1991–2020; a zone describes winter lows, not frost dates.
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.