USDA Hardiness Zone 9a
Frost Dates for 97420 — Coos Bay, Oregon
NOAA 1991–2020 normals from North Bend Regional Airport, OR (17 ft), 4 miles northwest.
Updated
In Coos Bay, the last spring frost (32°F) is around February 21 in half of years and has passed by March 25 in nine years out of ten. The first fall frost comes around December 9, as early as November 12 one year in ten, leaving a typical freeze-free season of 294 days (NOAA, North Bend Regional Airport, OR).
- Last spring frost
- February 21
- First fall frost
- December 9
- Growing season
- 294 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
- 35%
- Snow per year
- 0.2"
median, 1991–2020
median, 1991–2020
6 of 17 observed
NOAA normal
Frost risk by date in Coos Bay
Half of springs at North Bend Regional Airport, OR see their last 32°F night by February 21; only one in ten is past it by December 31, and one in ten still has one after March 25. Planting tender crops after March 5 leaves a 30% risk of a frost on them, after March 14 20%, and after March 25 10%. The 32 days between the even-odds date and the one-in-ten date is wider than at 92% 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 9 in half of years, as early as November 12 one year in ten, and holds off past January 28 one year in ten. A hard freeze of 28°F is less common: it came in 44% of winters. The freeze-free season lasts 294 days in a typical year, longer than at 95% of the 103 Oregon stations; it reaches 340 days one year in ten and falls short of 251 one year in ten. On average 10 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 40 days longer, to about April 2, and return around November 15. A 24°F night is unusual: 8% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 1 | Mar 15 | Mar 24 | Mar 29 | Apr 2 | Apr 8 | Apr 16 | Apr 23 | May 1 |
| 32°F95% of yrs | Dec 31 | Jan 26 | Feb 6 | Feb 13 | Feb 21 | Feb 26 | Mar 5 | Mar 14 | Mar 25 |
| 28°F44% of yrs | too rare for a date | ||||||||
| 24°F8% of yrs | too rare for a date | ||||||||
| 20°F2% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 24 | Oct 31 | Nov 5 | Nov 10 | Nov 15 | Nov 19 | Nov 25 | Dec 1 | Dec 11 |
| 32°F95% of yrs | Nov 12 | Nov 21 | Nov 27 | Dec 2 | Dec 9 | Dec 16 | Dec 25 | Jan 4 | Jan 28 |
| 28°F44% of yrs | too rare for a date | ||||||||
| 24°F8% of yrs | too rare for a date | ||||||||
| 20°F2% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at North Bend Regional Airport, 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 97420 →Compare Coos Bay with another place →
Weather by month in Coos Bay
August is the warmest month at North Bend Regional Airport, OR, averaging 67°F by day and 54°F at night; December is the coldest at 53°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 57% of years and March still brings one in 33% of years.
Warmth for growing adds up to 1,631 growing degree days a year (base 50°F), fewer than at 82% of the 103 Oregon stations. 30% of them (491) have built up by the end of June, and August adds the most, 324. Precipitation totals 59.3 inches a year, most in December (10.5") and least in July (0.4"); May to September bring 12% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 54 | 41 | 9.4 | 54% | 3 | 25 |
| Feb | 54 | 41 | 7.0 | 57% | 2 | 26 |
| Mar | 55 | 42 | 7.5 | 33% | 1 | 32 |
| Apr | 57 | 44 | 5.4 | 3% | <1 | 49 |
| May | 61 | 48 | 3.0 | 0% | 0 | 138 |
| Jun | 64 | 51 | 1.6 | 0% | 0 | 221 |
| Jul | 66 | 54 | 0.4 | 0% | 0 | 305 |
| Aug | 67 | 54 | 0.4 | 0% | 0 | 324 |
| Sep | 67 | 51 | 1.6 | 0% | 0 | 270 |
| Oct | 63 | 47 | 4.2 | 3% | 0 | 159 |
| Nov | 57 | 44 | 8.3 | 32% | 1 | 59 |
| Dec | 53 | 40 | 10.5 | 58% | 3 | 23 |
Monthly normals 1991–2020 at North Bend Regional Airport, OR (17 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, Coquille City, OR, 12 miles south of Coos Bay, has a last frost 35 days later (March 28), a first frost 33 days earlier (November 6), a season 69 days shorter.
When it snows in Coos Bay, Oregon
Measurable snow is rare here: only 6 of 17 winters from 1991 to 2020 recorded 0.1 inch or more at North Bend Regional Airport, OR, 4.2 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 97420
| When | What to do |
|---|---|
| December 13 – December 27 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| December 27 – January 10 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| January 24 – February 7 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| February 21 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 16 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 25 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 9 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 97420 is 4 miles from North Bend Regional Airport, OR, which stands at 17 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 97420 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.