USDA Hardiness Zone 8a
Frost Dates for 98648 — Stevenson, Washington
NOAA 1991–2020 normals from Cascade Locks, OR (142 ft), 2 miles east.
Updated
In Stevenson, the last spring frost (32°F) is around March 24 in half of years and has passed by April 16 in nine years out of ten. The first fall frost comes around November 20, as early as November 1 one year in ten, leaving a typical freeze-free season of 242 days (NOAA, Cascade Locks, OR).
- Last spring frost
- March 24
- First fall frost
- November 20
- Growing season
- 242 days
- Hardiness zone
- 8a
50% probability
50% probability
freeze-free, 50%
10 to 15°F (-12.2 to -9.4°C) coldest night
- First snow
- December 18
- Last snow
- February 4
- Winters with snow
- 78%
- Snow per year
- 10.3"
median, 1991–2020
median, 1991–2020
21 of 27 observed
NOAA normal
Frost risk by date in Stevenson
Half of springs at Cascade Locks, OR see their last 32°F night by March 24; only one in ten is past it by February 28, and one in ten still has one after April 16. Planting tender crops after March 31 leaves a 30% risk of a frost on them, after April 5 20%, and after April 16 10%. The 23 days between the even-odds date and the one-in-ten date is wider than at 81% of the 113 Washington 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 November 20 in half of years, as early as November 1 one year in ten, and holds off past December 12 one year in ten. A hard freeze of 28°F follows 19 days later, around December 9; in spring the one-in-ten date for 28°F is March 21, 26 days before the 32°F one. The freeze-free season lasts 242 days in a typical year, longer than at 88% of the 113 Washington stations; it reaches 273 days one year in ten and falls short of 211 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 26 days longer, to about April 19, and return around November 2. Nights of 24°F, cold enough to damage hardier plants, come in 83% of winters and 16°F in 23%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 1 | Apr 6 | Apr 11 | Apr 15 | Apr 19 | Apr 23 | Apr 27 | May 1 | May 6 |
| 32°F | Feb 28 | Mar 9 | Mar 14 | Mar 20 | Mar 24 | Mar 29 | Mar 31 | Apr 5 | Apr 16 |
| 28°F99% of yrs | Jan 10 | Jan 31 | Feb 10 | Feb 18 | Feb 24 | Feb 28 | Mar 6 | Mar 13 | Mar 21 |
| 24°F83% of yrs | Dec 13 | Dec 31 | Jan 7 | Jan 17 | Jan 28 | Feb 5 | Feb 14 | Feb 19 | Feb 27 |
| 20°F50% of yrs | too rare for a date | ||||||||
| 16°F23% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 18 | Oct 22 | Oct 26 | Oct 30 | Nov 2 | Nov 6 | Nov 10 | Nov 15 | Nov 23 |
| 32°F | Nov 1 | Nov 7 | Nov 11 | Nov 15 | Nov 20 | Nov 25 | Nov 30 | Dec 5 | Dec 12 |
| 28°F99% of yrs | Nov 13 | Nov 23 | Nov 30 | Dec 5 | Dec 9 | Dec 16 | Dec 21 | Dec 28 | Jan 7 |
| 24°F83% of yrs | Nov 26 | Dec 5 | Dec 11 | Dec 18 | Dec 26 | Jan 1 | Jan 7 | Jan 18 | Feb 10 |
| 20°F50% of yrs | too rare for a date | ||||||||
| 16°F23% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Cascade Locks, 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 98648 →Compare Stevenson with another place →
Compared with the next station
The nearest other station, Carson Fish Hatchery, WA, 14 miles north of Stevenson and 992 feet higher, has a last frost 39 days later (May 2), a first frost 42 days earlier (October 9), a season 81 days shorter.
When it snows in Stevenson, Washington
The first measurable snow (0.1 inch or more) in Stevenson usually arrives around December 18, and the last of the season around February 4. Those are the middle dates across the winters of 1991–2020 at Bonneville Dam, OR, 3 miles away: half of years saw snow earlier, half later. Snow fell in 78% of those winters. The last 32°F night of spring typically comes 48 days after the last snow.
Planting calendar for 98648
| When | What to do |
|---|---|
| January 13 – January 27 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| January 27 – February 10 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| February 24 – March 10 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| March 24 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 28 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 6 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 20 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 98648 is 2 miles from Cascade Locks, OR, which stands at 142 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 98648 in zone 8a, the band where the coldest night of the year averaged 10 to 15°F (-12.2 to -9.4°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across Washington →
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.