USDA Hardiness Zone 4a
Frost Dates for 58540 — Garrison, North Dakota
NOAA 1991–2020 normals from Garrison, ND (1,910 ft), 4 miles east.
Updated
In Garrison, the last spring frost (32°F) is around May 14 in half of years and has passed by May 28 in nine years out of ten. The first fall frost comes around September 26, as early as September 13 one year in ten, leaving a typical freeze-free season of 133 days (NOAA, Garrison, ND).
- Last spring frost
- May 14
- First fall frost
- September 26
- Growing season
- 133 days
- Hardiness zone
- 4a
50% probability
50% probability
freeze-free, 50%
-30 to -25°F (-34.4 to -31.7°C) coldest night
- First snow
- October 30
- Last snow
- April 11
- Winters with snow
- 100%
- Snow per year
- 42.7"
median, 1991–2020
median, 1991–2020
23 of 23 observed
NOAA normal
Frost risk by date in Garrison
Half of springs at Garrison, ND see their last 32°F night by May 14; only one in ten is past it by May 2, and one in ten still has one after May 28. Planting tender crops after May 19 leaves a 30% risk of a frost on them, after May 22 20%, and after May 28 10%. The 14 days between the even-odds date and the one-in-ten date is wider than at 82% of the 33 North Dakota stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 26 in half of years, as early as September 13 one year in ten, and holds off past October 9 one year in ten. A hard freeze of 28°F follows 8 days later, around October 4; in spring the one-in-ten date for 28°F is May 17, 11 days before the 32°F one. The freeze-free season lasts 133 days in a typical year, shorter than at 73% of the 33 North Dakota stations; it reaches 151 days one year in ten and falls short of 114 one year in ten. On average 186 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 11 days longer, to about May 25, and return around September 17. Severe cold of 16°F or below comes every winter, usually between November 1 and April 7.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 12 | May 16 | May 19 | May 22 | May 25 | May 27 | May 30 | Jun 2 | Jun 6 |
| 32°F | May 2 | May 6 | May 8 | May 11 | May 14 | May 17 | May 19 | May 22 | May 28 |
| 28°F | Apr 22 | Apr 26 | Apr 29 | May 1 | May 3 | May 6 | May 8 | May 12 | May 17 |
| 24°F | Apr 11 | Apr 16 | Apr 19 | Apr 22 | Apr 25 | Apr 28 | Apr 30 | May 2 | May 6 |
| 20°F | Apr 3 | Apr 7 | Apr 10 | Apr 13 | Apr 16 | Apr 19 | Apr 21 | Apr 25 | Apr 30 |
| 16°F | Mar 24 | Mar 31 | Apr 2 | Apr 5 | Apr 7 | Apr 10 | Apr 13 | Apr 16 | Apr 21 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 2 | Sep 8 | Sep 12 | Sep 15 | Sep 17 | Sep 20 | Sep 22 | Sep 25 | Sep 29 |
| 32°F | Sep 13 | Sep 17 | Sep 21 | Sep 23 | Sep 26 | Sep 29 | Oct 1 | Oct 4 | Oct 9 |
| 28°F | Sep 20 | Sep 26 | Sep 29 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 14 | Oct 18 |
| 24°F | Sep 29 | Oct 3 | Oct 6 | Oct 9 | Oct 13 | Oct 16 | Oct 19 | Oct 23 | Oct 27 |
| 20°F | Oct 7 | Oct 12 | Oct 16 | Oct 20 | Oct 23 | Oct 26 | Oct 29 | Nov 1 | Nov 6 |
| 16°F | Oct 16 | Oct 22 | Oct 26 | Oct 29 | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 14 |
Freeze probabilities 1991–2020 at Garrison, ND, 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 58540 →Compare Garrison with another place →
Weather by month in Garrison
July is the warmest month at Garrison, ND, averaging 81°F by day and 56°F at night; January is the coldest at 21°F and 2°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month.
Warmth for growing adds up to 2,000 growing degree days a year (base 50°F), fewer than at 73% of the 33 North Dakota stations. 29% of them (579) have built up by the end of June, and July adds the most, 561. Precipitation totals 17.8 inches a year, most in June (3.5") and least in February (0.5"); May to September bring 69% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 21 | 2 | 0.6 | 100% | 31 | 0 |
| Feb | 25 | 5 | 0.5 | 100% | 28 | 0 |
| Mar | 37 | 17 | 0.7 | 100% | 29 | 2 |
| Apr | 53 | 29 | 1.3 | 100% | 19 | 26 |
| May | 66 | 41 | 2.6 | 92% | 5 | 170 |
| Jun | 74 | 51 | 3.5 | 5% | 0 | 382 |
| Jul | 81 | 56 | 2.6 | 0% | 0 | 561 |
| Aug | 81 | 54 | 1.8 | 1% | 0 | 544 |
| Sep | 71 | 45 | 1.7 | 67% | 1 | 268 |
| Oct | 54 | 32 | 1.2 | 100% | 15 | 46 |
| Nov | 38 | 19 | 0.6 | 100% | 27 | 2 |
| Dec | 25 | 7 | 0.7 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Garrison, ND (1,910 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, Beulah 1 W, ND, 29 miles southwest of Garrison, has a last frost 7 days later (May 21), a first frost 6 days earlier (September 20), a season 12 days shorter.
When it snows in Garrison, North Dakota
The first measurable snow (0.1 inch or more) in Garrison usually arrives around October 30, and the last of the season around April 11. Those are the middle dates across the winters of 1991–2020 at Garrison, ND, 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 33 days after the last snow.
Planting calendar for 58540
| When | What to do |
|---|---|
| March 5 – March 19 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 19 – April 2 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 16 – April 30 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 14 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 4 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 12 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 26 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 58540 is 4 miles from Garrison, ND, which stands at 1,910 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 58540 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.
Frost dates across North Dakota →
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.