USDA Hardiness Zone 8b
Frost Dates for 97229 — Portland, Oregon
NOAA 1991–2020 normals from Nature Park-Beaverton, OR (185 ft), 3 miles south.
Updated
In Portland, the last spring frost (32°F) is around February 11 in half of years and has passed by March 5 in nine years out of ten. The first fall frost comes around December 5, as early as November 11 one year in ten, leaving a typical freeze-free season of 303 days (NOAA, Nature Park-Beaverton, OR).
- Last spring frost
- February 11
- First fall frost
- December 5
- Growing season
- 303 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
- 25%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
4 of 16 observed
NOAA normal
Frost risk by date in Portland
Half of springs at Nature Park-Beaverton, OR see their last 32°F night by February 11; only one in ten is past it by December 26, and one in ten still has one after March 5. Planting tender crops after February 22 leaves a 30% risk of a frost on them, after February 27 20%, and after March 5 10%. The 22 days between the even-odds date and the one-in-ten date is narrower than at 45% 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 5 in half of years, as early as November 11 one year in ten, and holds off past January 12 one year in ten. A hard freeze of 28°F follows 16 days later, around December 21; in spring the one-in-ten date for 28°F is February 16, 17 days before the 32°F one. The freeze-free season lasts 303 days in a typical year, longer than at 96% of the 103 Oregon stations; it reaches 344 days one year in ten and falls short of 264 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 March 23, and return around November 13. A 24°F night is unusual: 15% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Feb 25 | Mar 4 | Mar 11 | Mar 18 | Mar 23 | Mar 26 | Mar 31 | Apr 6 | Apr 15 |
| 32°F97% of yrs | Dec 26 | Jan 9 | Jan 25 | Feb 3 | Feb 11 | Feb 17 | Feb 22 | Feb 27 | Mar 5 |
| 28°F56% of yrs | Dec 2 | Dec 12 | Dec 22 | Jan 1 | Jan 6 | Jan 16 | Jan 28 | Feb 6 | Feb 16 |
| 24°F15% of yrs | too rare for a date | ||||||||
| 20°F4% of yrs | too rare for a date | ||||||||
| 16°F0% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 26 | Nov 1 | Nov 5 | Nov 10 | Nov 13 | Nov 17 | Nov 22 | Nov 28 | Dec 4 |
| 32°F97% of yrs | Nov 11 | Nov 18 | Nov 24 | Nov 30 | Dec 5 | Dec 10 | Dec 18 | Dec 29 | Jan 12 |
| 28°F56% of yrs | Nov 24 | Dec 1 | Dec 7 | Dec 12 | Dec 21 | Dec 31 | Jan 6 | Jan 19 | Feb 5 |
| 24°F15% of yrs | too rare for a date | ||||||||
| 20°F4% of yrs | too rare for a date | ||||||||
| 16°F0% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Nature Park-Beaverton, 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 97229 →Compare Portland with another place →
Weather by month in Portland
August is the warmest month at Nature Park-Beaverton, OR, averaging 82°F by day and 57°F at night; December is the coldest at 49°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 56% of years and March still brings one in 14% of years.
Warmth for growing adds up to 2,763 growing degree days a year (base 50°F), more than at 83% of the 103 Oregon stations. 33% of them (916) have built up by the end of June, and August adds the most, 601. Precipitation totals 39.3 inches a year, most in December (6.3") and least in July (0.5"); May to September bring 16% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 50 | 40 | 5.5 | 62% | 3 | 11 |
| Feb | 54 | 40 | 4.3 | 56% | 1 | 22 |
| Mar | 58 | 42 | 4.1 | 14% | <1 | 52 |
| Apr | 63 | 45 | 3.0 | 0% | 0 | 133 |
| May | 70 | 50 | 2.2 | 0% | 0 | 302 |
| Jun | 73 | 53 | 1.7 | 0% | 0 | 398 |
| Jul | 81 | 57 | 0.5 | 0% | 0 | 576 |
| Aug | 82 | 57 | 0.5 | 0% | 0 | 601 |
| Sep | 76 | 53 | 1.4 | 0% | 0 | 426 |
| Oct | 65 | 47 | 3.9 | 3% | 0 | 193 |
| Nov | 55 | 43 | 5.9 | 39% | 1 | 42 |
| Dec | 49 | 40 | 6.3 | 67% | 4 | 9 |
Monthly normals 1991–2020 at Nature Park-Beaverton, OR (185 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, Beaverton 2 SSW, OR, 6 miles south of Portland, has a last frost 49 days later (April 1), a first frost 29 days earlier (November 6), a season 81 days shorter.
When it snows in Portland, Oregon
Measurable snow is rare here: only 4 of 16 winters from 1991 to 2020 recorded 0.1 inch or more at Beaverton 2 SSW, OR, 6 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 97229
| When | What to do |
|---|---|
| December 3 – December 17 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| December 17 – December 31 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| January 14 – January 28 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| February 11 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 12 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 21 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 5 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 97229 is 3 miles from Nature Park-Beaverton, OR, which stands at 185 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 97229 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.