USDA Hardiness Zone 3b
Frost Dates for 58368 — Rugby, North Dakota
NOAA 1991–2020 normals from Rugby, ND (1,550 ft), 6 miles north.
Updated
In Rugby, the last spring frost (32°F) is around May 17 in half of years and has passed by May 31 in nine years out of ten. The first fall frost comes around September 23, as early as September 11 one year in ten, leaving a typical freeze-free season of 129 days (NOAA, Rugby, ND).
- Last spring frost
- May 17
- First fall frost
- September 23
- Growing season
- 129 days
- Hardiness zone
- 3b
50% probability
50% probability
freeze-free, 50%
-35 to -30°F (-37.2 to -34.4°C) coldest night
- First snow
- November 2
- Last snow
- April 13
- Winters with snow
- 100%
- Snow per year
- 43.4"
median, 1991–2020
median, 1991–2020
20 of 20 observed
NOAA normal
Frost risk by date in Rugby
Half of springs at Rugby, ND see their last 32°F night by May 17; only one in ten is past it by May 3, and one in ten still has one after May 31. Planting tender crops after May 23 leaves a 30% risk of a frost on them, after May 26 20%, and after May 31 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 23 in half of years, as early as September 11 one year in ten, and holds off past October 5 one year in ten. A hard freeze of 28°F follows 8 days later, around October 1; in spring the one-in-ten date for 28°F is May 22, 9 days before the 32°F one. The freeze-free season lasts 129 days in a typical year, shorter than at 82% of the 33 North Dakota stations; it reaches 146 days one year in ten and falls short of 109 one year in ten. On average 195 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 9 days longer, to about May 26, and return around September 14. Severe cold of 16°F or below comes every winter, usually between October 29 and April 7.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 13 | May 17 | May 20 | May 24 | May 26 | May 29 | May 31 | Jun 3 | Jun 11 |
| 32°F | May 3 | May 8 | May 11 | May 14 | May 17 | May 20 | May 23 | May 26 | May 31 |
| 28°F | Apr 21 | Apr 27 | May 1 | May 3 | May 6 | May 9 | May 12 | May 16 | May 22 |
| 24°F | Apr 9 | Apr 15 | Apr 18 | Apr 23 | Apr 26 | Apr 30 | May 2 | May 5 | May 10 |
| 20°F | Apr 2 | Apr 6 | Apr 9 | Apr 13 | Apr 16 | Apr 19 | Apr 23 | Apr 27 | May 1 |
| 16°F | Mar 24 | Mar 30 | Apr 2 | Apr 4 | Apr 7 | Apr 11 | Apr 13 | Apr 17 | Apr 23 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 31 | Sep 4 | Sep 8 | Sep 11 | Sep 14 | Sep 17 | Sep 19 | Sep 22 | Sep 25 |
| 32°F | Sep 11 | Sep 15 | Sep 18 | Sep 21 | Sep 23 | Sep 25 | Sep 28 | Oct 1 | Oct 5 |
| 28°F | Sep 20 | Sep 24 | Sep 27 | Sep 29 | Oct 1 | Oct 4 | Oct 6 | Oct 9 | Oct 14 |
| 24°F | Sep 28 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 16 | Oct 20 | Oct 24 |
| 20°F | Oct 5 | Oct 10 | Oct 14 | Oct 17 | Oct 21 | Oct 24 | Oct 27 | Oct 30 | Nov 2 |
| 16°F | Oct 12 | Oct 19 | Oct 23 | Oct 27 | Oct 29 | Nov 1 | Nov 3 | Nov 6 | Nov 11 |
Freeze probabilities 1991–2020 at Rugby, 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 58368 →Compare Rugby with another place →
Weather by month in Rugby
July is the warmest month at Rugby, ND, averaging 80°F by day and 55°F at night; January is the coldest at 16°F and -4°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 1,910 growing degree days a year (base 50°F), fewer than at 88% of the 33 North Dakota stations. 31% of them (587) have built up by the end of June, and July adds the most, 542. Precipitation totals 21.0 inches a year, most in June (3.8") and least in January (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 | 16 | -4 | 0.5 | 100% | 31 | 0 |
| Feb | 21 | 0 | 0.5 | 100% | 28 | 0 |
| Mar | 34 | 14 | 0.9 | 100% | 30 | 1 |
| Apr | 52 | 28 | 1.3 | 100% | 20 | 26 |
| May | 66 | 40 | 3.0 | 94% | 6 | 170 |
| Jun | 75 | 51 | 3.8 | 8% | 0 | 390 |
| Jul | 80 | 55 | 3.7 | 0% | 0 | 542 |
| Aug | 80 | 53 | 2.2 | 1% | 0 | 507 |
| Sep | 70 | 44 | 1.8 | 77% | 2 | 233 |
| Oct | 54 | 30 | 1.4 | 100% | 18 | 40 |
| Nov | 35 | 16 | 0.9 | 100% | 29 | 1 |
| Dec | 21 | 3 | 1.0 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Rugby, ND (1,550 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, Harvey 4NE, ND, 33 miles south of Rugby, has a last frost 5 days earlier (May 12), a first frost 3 days later (September 26), a season 6 days longer.
When it snows in Rugby, North Dakota
The first measurable snow (0.1 inch or more) in Rugby usually arrives around November 2, and the last of the season around April 13. Those are the middle dates across the winters of 1991–2020 at Rugby, ND, 5.6 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 34 days after the last snow.
Planting calendar for 58368
| When | What to do |
|---|---|
| March 8 – March 22 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 22 – April 5 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 19 – May 3 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 17 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 1 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 9 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 23 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 58368 is 6 miles from Rugby, ND, which stands at 1,550 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 58368 in zone 3b, the band where the coldest night of the year averaged -35 to -30°F (-37.2 to -34.4°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.