USDA Hardiness Zone 4a
Frost Dates for 58554 — Mandan, North Dakota
NOAA 1991–2020 normals from Mandan Exp Stn, ND (1,750 ft), under a mile northwest.
Updated
In Mandan, the last spring frost (32°F) is around May 13 in half of years and has passed by May 26 in nine years out of ten. The first fall frost comes around September 27, as early as September 15 one year in ten, leaving a typical freeze-free season of 136 days (NOAA, Mandan Exp Stn, ND).
- Last spring frost
- May 13
- First fall frost
- September 27
- Growing season
- 136 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
- November 15
- Last snow
- March 24
- Winters with snow
- 95%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
18 of 19 observed
NOAA normal
Frost risk by date in Mandan
Half of springs at Mandan Exp Stn, ND see their last 32°F night by May 13; only one in ten is past it by May 1, and one in ten still has one after May 26. Planting tender crops after May 18 leaves a 30% risk of a frost on them, after May 21 20%, and after May 26 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 21% of the 33 North Dakota stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 27 in half of years, as early as September 15 one year in ten, and holds off past October 10 one year in ten. A hard freeze of 28°F follows 7 days later, around October 4; in spring the one-in-ten date for 28°F is May 17, 9 days before the 32°F one. The freeze-free season lasts 136 days in a typical year, shorter than at 52% of the 33 North Dakota stations; it reaches 154 days one year in ten and falls short of 118 one year in ten. On average 184 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 10 days longer, to about May 23, and return around September 19. Severe cold of 16°F or below comes every winter, usually between November 2 and April 6.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 10 | May 14 | May 17 | May 20 | May 23 | May 25 | May 28 | May 31 | Jun 4 |
| 32°F | May 1 | May 4 | May 7 | May 10 | May 13 | May 15 | May 18 | May 21 | May 26 |
| 28°F | Apr 19 | Apr 24 | Apr 28 | Apr 30 | May 3 | May 6 | May 9 | May 13 | May 17 |
| 24°F | Apr 9 | Apr 13 | Apr 17 | Apr 20 | Apr 23 | Apr 26 | Apr 29 | May 2 | May 7 |
| 20°F | Apr 2 | Apr 6 | Apr 8 | Apr 11 | Apr 14 | Apr 17 | Apr 19 | Apr 23 | Apr 28 |
| 16°F | Mar 20 | Mar 28 | Apr 1 | Apr 3 | Apr 6 | Apr 8 | Apr 11 | Apr 15 | Apr 20 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 6 | Sep 10 | Sep 14 | Sep 16 | Sep 19 | Sep 21 | Sep 24 | Sep 26 | Oct 1 |
| 32°F | Sep 15 | Sep 20 | Sep 23 | Sep 25 | Sep 27 | Sep 30 | Oct 2 | Oct 5 | Oct 10 |
| 28°F | Sep 23 | Sep 27 | Sep 30 | Oct 2 | Oct 4 | Oct 7 | Oct 10 | Oct 14 | Oct 19 |
| 24°F | Sep 30 | Oct 4 | Oct 7 | Oct 11 | Oct 14 | Oct 17 | Oct 20 | Oct 23 | Oct 27 |
| 20°F | Oct 7 | Oct 13 | Oct 18 | Oct 21 | Oct 24 | Oct 27 | Oct 30 | Nov 1 | Nov 7 |
| 16°F | Oct 19 | Oct 24 | Oct 28 | Oct 31 | Nov 2 | Nov 5 | Nov 8 | Nov 11 | Nov 16 |
Freeze probabilities 1991–2020 at Mandan Exp Stn, 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 58554 →Compare Mandan with another place →
Weather by month in Mandan
July is the warmest month at Mandan Exp Stn, ND, averaging 83°F by day and 58°F at night; January is the coldest at 23°F and 3°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 2,242 growing degree days a year (base 50°F), more than at 64% of the 33 North Dakota stations. 30% of them (682) have built up by the end of June, and July adds the most, 629. Precipitation totals 18.3 inches a year, most in June (3.4") and least in January (0.4"); May to September bring 71% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 23 | 3 | 0.4 | 100% | 31 | 0 |
| Feb | 27 | 6 | 0.4 | 100% | 28 | 0 |
| Mar | 40 | 18 | 0.6 | 100% | 28 | 5 |
| Apr | 54 | 30 | 1.3 | 100% | 17 | 39 |
| May | 67 | 43 | 2.6 | 90% | 4 | 201 |
| Jun | 76 | 53 | 3.4 | 3% | 0 | 437 |
| Jul | 83 | 58 | 3.2 | 0% | 0 | 629 |
| Aug | 82 | 56 | 2.2 | 0% | 0 | 579 |
| Sep | 72 | 46 | 1.6 | 63% | 2 | 293 |
| Oct | 56 | 32 | 1.5 | 100% | 16 | 57 |
| Nov | 40 | 19 | 0.6 | 100% | 28 | 3 |
| Dec | 27 | 8 | 0.5 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Mandan Exp Stn, ND (1,750 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, Bismarck 2.4 NNW, ND, 6 miles east of Mandan, has a last frost 3 days earlier (May 10), a first frost 3 days later (September 30), a season 6 days longer.
When it snows in Mandan, North Dakota
The first measurable snow (0.1 inch or more) in Mandan usually arrives around November 15, and the last of the season around March 24. Those are the middle dates across the winters of 1991–2020 at Mandan Exp Stn, ND, 0.1 miles away: half of years saw snow earlier, half later. Snow fell in 95% of those winters. The last 32°F night of spring typically comes 50 days after the last snow.
Planting calendar for 58554
| When | What to do |
|---|---|
| March 4 – March 18 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 18 – April 1 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 15 – April 29 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 13 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 5 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 13 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 27 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 58554 is under a mile from Mandan Exp Stn, ND, which stands at 1,750 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 58554 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.