USDA Hardiness Zone 8b
Frost Dates for 98570 — Onalaska, Washington
NOAA 1991–2020 normals from Mayfield Pwr Plt, WA (280 ft), 7 miles southeast.
Updated
In Onalaska, the last spring frost (32°F) is around April 7 in half of years and has passed by May 8 in nine years out of ten. The first fall frost comes around November 13, as early as October 24 one year in ten, leaving a typical freeze-free season of 215 days (NOAA, Mayfield Pwr Plt, WA).
- Last spring frost
- April 7
- First fall frost
- November 13
- Growing season
- 215 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
- 43%
- Snow per year
- 3.4"
median, 1991–2020
median, 1991–2020
12 of 28 observed
NOAA normal
Frost risk by date in Onalaska
Half of springs at Mayfield Pwr Plt, WA see their last 32°F night by April 7; only one in ten is past it by March 16, and one in ten still has one after May 8. Planting tender crops after April 24 leaves a 30% risk of a frost on them, after April 30 20%, and after May 8 10%. The 31 days between the even-odds date and the one-in-ten date is wider than at 98% 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 13 in half of years, as early as October 24 one year in ten, and holds off past December 4 one year in ten. A hard freeze of 28°F follows 18 days later, around December 1; in spring the one-in-ten date for 28°F is April 2, 36 days before the 32°F one. The freeze-free season lasts 215 days in a typical year, longer than at 69% of the 113 Washington stations; it reaches 249 days one year in ten and falls short of 181 one year in ten. On average 66 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 29 days longer, to about May 6, and return around October 24. Nights of 24°F, cold enough to damage hardier plants, come in 85% of winters and 16°F in 14%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 17 | Apr 24 | Apr 28 | May 2 | May 6 | May 10 | May 14 | May 17 | May 23 |
| 32°F | Mar 16 | Mar 24 | Mar 29 | Apr 2 | Apr 7 | Apr 15 | Apr 24 | Apr 30 | May 8 |
| 28°F | Jan 31 | Feb 16 | Feb 24 | Feb 28 | Mar 6 | Mar 13 | Mar 19 | Mar 24 | Apr 2 |
| 24°F85% of yrs | Dec 12 | Dec 31 | Jan 7 | Jan 18 | Jan 31 | Feb 8 | Feb 16 | Feb 24 | Mar 1 |
| 20°F43% of yrs | too rare for a date | ||||||||
| 16°F14% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 4 | Oct 12 | Oct 17 | Oct 20 | Oct 24 | Oct 27 | Oct 30 | Nov 4 | Nov 11 |
| 32°F | Oct 24 | Oct 30 | Nov 5 | Nov 9 | Nov 13 | Nov 17 | Nov 22 | Nov 27 | Dec 4 |
| 28°F | Nov 8 | Nov 16 | Nov 23 | Nov 27 | Dec 1 | Dec 5 | Dec 13 | Dec 20 | Jan 1 |
| 24°F85% of yrs | Nov 23 | Nov 30 | Dec 5 | Dec 11 | Dec 19 | Dec 25 | Jan 2 | Jan 20 | Feb 7 |
| 20°F43% of yrs | too rare for a date | ||||||||
| 16°F14% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Mayfield Pwr Plt, WA, 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 98570 →Compare Onalaska with another place →
Weather by month in Onalaska
August is the warmest month at Mayfield Pwr Plt, WA, averaging 81°F by day and 52°F at night; December is the coldest at 44°F and 34°F. A freezing night is all but certain in every month from December 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 55% of years and May still brings one in 19% of years.
Warmth for growing adds up to 2,054 growing degree days a year (base 50°F), more than at 55% of the 113 Washington stations. 29% of them (587) have built up by the end of June, and August adds the most, 508. Precipitation totals 58.8 inches a year, most in November (8.4") and least in July (0.9"); May to September bring 19% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 45 | 33 | 8.1 | 99% | 14 | 0 |
| Feb | 49 | 34 | 5.8 | 97% | 13 | 1 |
| Mar | 54 | 35 | 6.3 | 97% | 11 | 12 |
| Apr | 60 | 39 | 5.5 | 55% | 3 | 62 |
| May | 69 | 43 | 3.8 | 19% | 1 | 209 |
| Jun | 72 | 48 | 2.7 | 0% | 0 | 303 |
| Jul | 81 | 51 | 0.9 | 0% | 0 | 504 |
| Aug | 81 | 52 | 1.3 | 0% | 0 | 508 |
| Sep | 74 | 48 | 2.5 | 0% | 0 | 337 |
| Oct | 62 | 43 | 5.4 | 23% | 1 | 104 |
| Nov | 51 | 38 | 8.4 | 82% | 8 | 12 |
| Dec | 44 | 34 | 8.1 | 100% | 15 | 2 |
Monthly normals 1991–2020 at Mayfield Pwr Plt, WA (280 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, Toledo Faa Airport, WA, 11 miles southwest of Onalaska, has a last frost 2 days earlier (April 5), a first frost 19 days earlier (October 25), a season 19 days shorter.
When it snows in Onalaska, Washington
Measurable snow is rare here: only 12 of 28 winters from 1991 to 2020 recorded 0.1 inch or more at Mayfield Pwr Plt, WA, 6.8 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 98570
| When | What to do |
|---|---|
| January 27 – February 10 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 10 – February 24 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 10 – March 24 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 7 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 21 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 30 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 13 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 98570 is 7 miles from Mayfield Pwr Plt, WA, which stands at 280 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 98570 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.
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.