USDA Hardiness Zone 6a
Frost Dates for 99148 — Loon Lake, Washington
NOAA 1991–2020 normals from Deer Park Airport, WA (2,191 ft), 12 miles southeast.
Updated
In Loon Lake, the last spring frost (32°F) is around May 22 in half of years and has passed by June 15 in nine years out of ten. The first fall frost comes around September 14, as early as August 28 one year in ten, leaving a typical freeze-free season of 112 days (NOAA, Deer Park Airport, WA).
- Last spring frost
- May 22
- First fall frost
- September 14
- Growing season
- 112 days
- Hardiness zone
- 6a
50% probability
50% probability
freeze-free, 50%
-10 to -5°F (-23.3 to -20.6°C) coldest night
- First snow
- November 25
- Last snow
- March 6
- Winters with snow
- 100%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
16 of 16 observed
NOAA normal
Frost risk by date in Loon Lake
Half of springs at Deer Park Airport, WA see their last 32°F night by May 22; only one in ten is past it by May 2, and one in ten still has one after June 15. Planting tender crops after May 31 leaves a 30% risk of a frost on them, after June 5 20%, and after June 15 10%. The 24 days between the even-odds date and the one-in-ten date is wider than at 86% 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 September 14 in half of years, as early as August 28 one year in ten, and holds off past October 1 one year in ten. A hard freeze of 28°F follows 15 days later, around September 29; in spring the one-in-ten date for 28°F is May 21, 25 days before the 32°F one. The freeze-free season lasts 112 days in a typical year, shorter than at 97% of the 113 Washington stations; it reaches 140 days one year in ten and falls short of 84 one year in ten. On average 174 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between November 10 and March 6.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | May 2 | May 8 | May 13 | May 17 | May 22 | May 27 | May 31 | Jun 5 | Jun 15 |
| 28°F | Apr 18 | Apr 23 | Apr 28 | Apr 30 | May 3 | May 6 | May 11 | May 14 | May 21 |
| 24°F | Mar 24 | Mar 31 | Apr 7 | Apr 14 | Apr 19 | Apr 22 | Apr 27 | May 1 | May 7 |
| 20°F | Mar 5 | Mar 10 | Mar 14 | Mar 19 | Mar 24 | Mar 29 | Apr 3 | Apr 9 | Apr 20 |
| 16°F | Feb 16 | Feb 24 | Feb 28 | Mar 3 | Mar 6 | Mar 8 | Mar 12 | Mar 16 | Mar 24 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | Aug 28 | Sep 3 | Sep 7 | Sep 10 | Sep 14 | Sep 18 | Sep 21 | Sep 25 | Oct 1 |
| 28°F | Sep 14 | Sep 19 | Sep 23 | Sep 27 | Sep 29 | Oct 1 | Oct 4 | Oct 7 | Oct 14 |
| 24°F | Sep 27 | Oct 1 | Oct 3 | Oct 6 | Oct 10 | Oct 15 | Oct 20 | Oct 25 | Nov 3 |
| 20°F | Oct 5 | Oct 12 | Oct 17 | Oct 23 | Oct 27 | Oct 31 | Nov 5 | Nov 11 | Nov 20 |
| 16°F | Oct 18 | Oct 26 | Oct 31 | Nov 4 | Nov 10 | Nov 14 | Nov 20 | Nov 25 | Dec 2 |
Freeze probabilities 1991–2020 at Deer Park Airport, 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 99148 →Compare Loon Lake with another place →
Weather by month in Loon Lake
July is the warmest month at Deer Park Airport, WA, averaging 84°F by day and 48°F at night; December is the coldest at 33°F and 21°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). July is the only month with under a 10% chance of a 32°F night. In spring, May still brings one in 89% of years and June still brings one in 26% of years.
Warmth for growing adds up to 1,685 growing degree days a year (base 50°F), fewer than at 81% of the 113 Washington stations. 26% of them (436) have built up by the end of June, and July adds the most, 505. Precipitation totals 22.5 inches a year, most in December (3.1") and least in July (0.6"); May to September bring 26% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 34 | 21 | 2.9 | 100% | 28 | 0 |
| Feb | 39 | 22 | 1.6 | 100% | 25 | 0 |
| Mar | 49 | 27 | 2.3 | 100% | 25 | 1 |
| Apr | 58 | 32 | 1.9 | 100% | 18 | 26 |
| May | 67 | 39 | 1.9 | 89% | 7 | 146 |
| Jun | 73 | 44 | 1.9 | 26% | 1 | 262 |
| Jul | 84 | 48 | 0.6 | 3% | <1 | 505 |
| Aug | 84 | 47 | 0.7 | 15% | <1 | 481 |
| Sep | 74 | 40 | 0.8 | 86% | 4 | 228 |
| Oct | 58 | 32 | 2.0 | 100% | 17 | 35 |
| Nov | 42 | 26 | 2.8 | 100% | 22 | 1 |
| Dec | 33 | 21 | 3.1 | 100% | 28 | 0 |
Monthly normals 1991–2020 at Deer Park Airport, WA (2,191 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, Chewelah, WA, 13 miles northwest of Loon Lake and 521 feet lower, has a last frost 6 days earlier (May 16), a first frost 1 day later (September 15), a season 8 days longer.
When it snows in Loon Lake, Washington
The first measurable snow (0.1 inch or more) in Loon Lake usually arrives around November 25, and the last of the season around March 6. Those are the middle dates across the winters of 1991–2020 at Chewelah, WA, 13.5 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 77 days after the last snow.
Planting calendar for 99148
| When | What to do |
|---|---|
| March 13 – March 27 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 27 – April 10 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 24 – May 8 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 22 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by June 22 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by August 31 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 14 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 99148 is 12 miles from Deer Park Airport, WA, which stands at 2,191 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station; its figures are presented in full for 99006 (Deer Park). The 2023 USDA Plant Hardiness Zone Map lists ZIP 99148 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°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.