USDA Hardiness Zone 8b
Frost Dates for 97386 — Sweet Home, Oregon
NOAA 1991–2020 normals from Foster Dam, OR (550 ft), 3 miles northeast.
Updated
In Sweet Home, the last spring frost (32°F) is around April 12 in half of years and has passed by May 5 in nine years out of ten. The first fall frost comes around October 28, as early as October 5 one year in ten, leaving a typical freeze-free season of 197 days (NOAA, Foster Dam, OR).
- Last spring frost
- April 12
- First fall frost
- October 28
- Growing season
- 197 days
- Hardiness zone
- 8b
50% probability
50% probability
freeze-free, 50%
15 to 20°F (-9.4 to -6.7°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 4%
- Snow per year
- 0.1"
median, 1991–2020
median, 1991–2020
1 of 27 observed
NOAA normal
Frost risk by date in Sweet Home
Half of springs at Foster Dam, OR see their last 32°F night by April 12; only one in ten is past it by March 16, and one in ten still has one after May 5. Planting tender crops after April 24 leaves a 30% risk of a frost on them, after April 30 20%, and after May 5 10%. The 23 days between the even-odds date and the one-in-ten date is wider than at 56% 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 October 28 in half of years, as early as October 5 one year in ten, and holds off past November 21 one year in ten. A hard freeze of 28°F follows 21 days later, around November 18; in spring the one-in-ten date for 28°F is April 11, 24 days before the 32°F one. The freeze-free season lasts 197 days in a typical year, longer than at 50% of the 103 Oregon stations; it reaches 233 days one year in ten and falls short of 165 one year in ten. On average 55 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 24 days longer, to about May 6, and return around October 6. Nights of 24°F, cold enough to damage hardier plants, come in 95% of winters and 16°F in 22%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 17 | Apr 26 | Apr 30 | May 3 | May 6 | May 10 | May 13 | May 17 | May 25 |
| 32°F | Mar 16 | Mar 26 | Apr 1 | Apr 6 | Apr 12 | Apr 18 | Apr 24 | Apr 30 | May 5 |
| 28°F | Feb 12 | Feb 20 | Feb 27 | Mar 3 | Mar 9 | Mar 14 | Mar 21 | Mar 28 | Apr 11 |
| 24°F95% of yrs | Dec 22 | Jan 6 | Jan 20 | Jan 31 | Feb 9 | Feb 16 | Feb 21 | Feb 28 | Mar 6 |
| 20°F60% of yrs | Dec 4 | Dec 16 | Dec 24 | Jan 1 | Jan 7 | Jan 17 | Jan 30 | Feb 12 | Feb 21 |
| 16°F22% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 14 | Sep 20 | Sep 27 | Oct 2 | Oct 6 | Oct 10 | Oct 15 | Oct 20 | Oct 27 |
| 32°F | Oct 5 | Oct 14 | Oct 20 | Oct 24 | Oct 28 | Nov 1 | Nov 6 | Nov 13 | Nov 21 |
| 28°F | Oct 25 | Nov 1 | Nov 6 | Nov 13 | Nov 18 | Nov 23 | Nov 30 | Dec 5 | Dec 16 |
| 24°F95% of yrs | Nov 8 | Nov 17 | Nov 27 | Dec 2 | Dec 8 | Dec 16 | Dec 24 | Jan 1 | Jan 18 |
| 20°F60% of yrs | Nov 20 | Dec 1 | Dec 7 | Dec 14 | Dec 21 | Dec 30 | Jan 4 | Jan 16 | Feb 7 |
| 16°F22% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Foster Dam, 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 97386 →Compare Sweet Home with another place →
Weather by month in Sweet Home
August is the warmest month at Foster Dam, OR, averaging 83°F by day and 50°F at night; December is the coldest at 47°F and 34°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 64% of years and May still brings one in 19% of years.
Warmth for growing adds up to 2,111 growing degree days a year (base 50°F), fewer than at 56% of the 103 Oregon stations. 28% of them (595) have built up by the end of June, and August adds the most, 510. Precipitation totals 54.5 inches a year, most in December (8.4") and least in July (0.5"); May to September bring 17% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 48 | 34 | 7.2 | 99% | 13 | 3 |
| Feb | 51 | 35 | 5.6 | 100% | 11 | 6 |
| Mar | 56 | 37 | 6.3 | 94% | 7 | 25 |
| Apr | 60 | 40 | 5.4 | 64% | 2 | 64 |
| May | 67 | 44 | 3.8 | 19% | 1 | 185 |
| Jun | 73 | 48 | 2.5 | 0% | 0 | 313 |
| Jul | 82 | 51 | 0.5 | 0% | 0 | 507 |
| Aug | 83 | 50 | 0.6 | 0% | 0 | 510 |
| Sep | 76 | 47 | 2.0 | 5% | <1 | 349 |
| Oct | 64 | 42 | 4.6 | 56% | 2 | 127 |
| Nov | 53 | 38 | 7.6 | 91% | 8 | 21 |
| Dec | 47 | 34 | 8.4 | 100% | 12 | 4 |
Monthly normals 1991–2020 at Foster Dam, OR (550 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, Lebanon, OR, 13 miles northwest of Sweet Home and 220 feet lower, has a last frost 29 days earlier (March 14), a first frost 21 days later (November 18), a season 51 days longer.
When it snows in Sweet Home, Oregon
Measurable snow is rare here: only 1 of 27 winters from 1991 to 2020 recorded 0.1 inch or more at Foster Dam, OR, 3.1 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 97386
| When | What to do |
|---|---|
| February 1 – February 15 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 15 – March 1 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 15 – March 29 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 12 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 5 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 14 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 28 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 97386 is 3 miles from Foster Dam, OR, which stands at 550 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 97386 in zone 8b, the band where the coldest night of the year averaged 15 to 20°F (-9.4 to -6.7°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.