USDA Hardiness Zone 4a
Frost Dates for 99576 — Dillingham, Alaska
NOAA 1991–2020 normals from King Salmon, AK (63 ft), 70 miles east.
Updated
In Dillingham, the last spring frost (32°F) is around May 26 in half of years and has passed by June 11 in nine years out of ten. The first fall frost comes around September 15, as early as August 31 one year in ten, leaving a typical freeze-free season of 111 days (NOAA, King Salmon, AK).
- Last spring frost
- May 26
- First fall frost
- September 15
- Growing season
- 111 days
- Hardiness zone
- 4a
50% probability
50% probability
freeze-free, 50%
-30 to -25°F (-34.4 to -31.7°C) coldest night
Frost risk by date in Dillingham
Half of springs at King Salmon, AK see their last 32°F night by May 26; only one in ten is past it by May 9, and one in ten still has one after June 11. Planting tender crops after May 31 leaves a 30% risk of a frost on them, after June 4 20%, and after June 11 10%. The 16 days between the even-odds date and the one-in-ten date is wider than at 79% of the 38 Alaska stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 15 in half of years, as early as August 31 one year in ten, and holds off past September 29 one year in ten. A hard freeze of 28°F follows 12 days later, around September 27; in spring the one-in-ten date for 28°F is May 25, 17 days before the 32°F one. The freeze-free season lasts 111 days in a typical year, shorter than at 79% of the 38 Alaska stations; it reaches 133 days one year in ten and falls short of 89 one year in ten. On average 192 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 19 days longer, to about June 14, and return around September 1. Severe cold of 16°F or below comes every winter, usually between October 23 and April 9.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 31 | Jun 4 | Jun 7 | Jun 11 | Jun 14 | Jun 17 | Jun 21 | Jun 26 | Jul 4 |
| 32°F | May 9 | May 15 | May 19 | May 23 | May 26 | May 29 | May 31 | Jun 4 | Jun 11 |
| 28°F | Apr 23 | Apr 29 | May 2 | May 5 | May 8 | May 11 | May 14 | May 19 | May 25 |
| 24°F | Apr 11 | Apr 16 | Apr 19 | Apr 22 | Apr 26 | Apr 29 | May 1 | May 4 | May 9 |
| 20°F | Apr 4 | Apr 7 | Apr 11 | Apr 14 | Apr 16 | Apr 20 | Apr 22 | Apr 25 | Apr 30 |
| 16°F | Mar 30 | Apr 2 | Apr 4 | Apr 6 | Apr 9 | Apr 11 | Apr 14 | Apr 18 | Apr 22 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 16 | Aug 21 | Aug 25 | Aug 29 | Sep 1 | Sep 3 | Sep 6 | Sep 11 | Sep 16 |
| 32°F | Aug 31 | Sep 4 | Sep 7 | Sep 11 | Sep 15 | Sep 17 | Sep 20 | Sep 24 | Sep 29 |
| 28°F | Sep 11 | Sep 17 | Sep 20 | Sep 24 | Sep 27 | Sep 29 | Oct 1 | Oct 4 | Oct 10 |
| 24°F | Sep 23 | Sep 27 | Oct 1 | Oct 2 | Oct 5 | Oct 8 | Oct 11 | Oct 16 | Oct 21 |
| 20°F | Oct 1 | Oct 4 | Oct 8 | Oct 11 | Oct 14 | Oct 18 | Oct 21 | Oct 25 | Oct 31 |
| 16°F | Oct 6 | Oct 12 | Oct 16 | Oct 20 | Oct 23 | Oct 26 | Oct 29 | Nov 1 | Nov 7 |
Freeze probabilities 1991–2020 at King Salmon, AK, 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 99576 →Compare Dillingham with another place →
Weather by month in Dillingham
July is the warmest month at King Salmon, AK, averaging 65°F by day and 49°F at night; January is the coldest at 24°F and 10°F. A freezing night is all but certain in every month from September to May (a 90% chance or more). July is the only month with under a 10% chance of a 32°F night. In spring, June still brings one in 30% of years.
Warmth for growing adds up to 566 growing degree days a year (base 50°F), fewer than at 63% of the 38 Alaska stations. 22% of them (124) have built up by the end of June, and July adds the most, 212. Precipitation totals 21.4 inches a year, most in September (3.4") and least in March (0.8"); May to September bring 58% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 24 | 10 | 0.9 | 100% | 27 | 0 |
| Feb | 30 | 15 | 0.9 | 100% | 25 | 0 |
| Mar | 32 | 15 | 0.8 | 100% | 28 | 0 |
| Apr | 45 | 28 | 1.0 | 100% | 23 | 1 |
| May | 55 | 36 | 1.4 | 98% | 10 | 13 |
| Jun | 62 | 44 | 1.8 | 30% | 1 | 109 |
| Jul | 65 | 49 | 2.5 | 0% | 0 | 212 |
| Aug | 63 | 48 | 3.3 | 10% | <1 | 179 |
| Sep | 56 | 41 | 3.4 | 91% | 6 | 48 |
| Oct | 44 | 29 | 2.3 | 100% | 20 | 3 |
| Nov | 32 | 18 | 1.7 | 100% | 25 | 0 |
| Dec | 26 | 11 | 1.4 | 100% | 28 | 0 |
Monthly normals 1991–2020 at King Salmon, AK (63 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Planting calendar for 99576
| When | What to do |
|---|---|
| March 17 – March 31 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 31 – April 14 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 28 – May 12 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 26 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by June 23 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 1 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 15 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 99576 is 70 miles from King Salmon, AK, which stands at 63 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. That is farther than 25 miles, so local frost can differ noticeably from these figures. The 2023 USDA Plant Hardiness Zone Map lists ZIP 99576 in zone 4a, the band where the coldest night of the year averaged -30 to -25°F (-34.4 to -31.7°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.