USDA Hardiness Zone 5a
Frost Dates for 59019 — Columbus, Montana
NOAA 1991–2020 normals from Columbus, MT (3,602 ft), 3 miles north.
Updated
In Columbus, the last spring frost (32°F) is around May 27 in half of years and has passed by June 12 in nine years out of ten. The first fall frost comes around September 14, as early as September 1 one year in ten, leaving a typical freeze-free season of 108 days (NOAA, Columbus, MT).
- Last spring frost
- May 27
- First fall frost
- September 14
- Growing season
- 108 days
- Hardiness zone
- 5a
50% probability
50% probability
freeze-free, 50%
-20 to -15°F (-28.9 to -26.1°C) coldest night
- First snow
- October 19
- Last snow
- April 25
- Winters with snow
- 89%
- Snow per year
- 47.6"
median, 1991–2020
median, 1991–2020
24 of 27 observed
NOAA normal
Frost risk by date in Columbus
Half of springs at Columbus, MT see their last 32°F night by May 27; only one in ten is past it by May 14, and one in ten still has one after June 12. Planting tender crops after June 1 leaves a 30% risk of a frost on them, after June 5 20%, and after June 12 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 40% of the 68 Montana stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 14 in half of years, as early as September 1 one year in ten, and holds off past September 28 one year in ten. A hard freeze of 28°F follows 12 days later, around September 26; in spring the one-in-ten date for 28°F is May 27, 16 days before the 32°F one. The freeze-free season lasts 108 days in a typical year, shorter than at 81% of the 68 Montana stations; it reaches 128 days one year in ten and falls short of 87 one year in ten. On average 183 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 16 days longer, to about June 12, and return around September 2. Severe cold of 16°F or below comes every winter, usually between October 28 and April 6.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 27 | Jun 1 | Jun 5 | Jun 9 | Jun 12 | Jun 16 | Jun 20 | Jun 24 | Jul 3 |
| 32°F | May 14 | May 18 | May 22 | May 25 | May 27 | May 30 | Jun 1 | Jun 5 | Jun 12 |
| 28°F | Apr 30 | May 5 | May 8 | May 11 | May 13 | May 16 | May 19 | May 23 | May 27 |
| 24°F | Apr 19 | Apr 23 | Apr 27 | Apr 29 | May 1 | May 4 | May 6 | May 9 | May 14 |
| 20°F | Apr 4 | Apr 11 | Apr 14 | Apr 17 | Apr 21 | Apr 24 | Apr 27 | Apr 30 | May 5 |
| 16°F | Mar 20 | Mar 26 | Mar 31 | Apr 3 | Apr 6 | Apr 10 | Apr 15 | Apr 19 | Apr 26 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 18 | Aug 24 | Aug 28 | Aug 31 | Sep 2 | Sep 4 | Sep 7 | Sep 10 | Sep 15 |
| 32°F | Sep 1 | Sep 5 | Sep 8 | Sep 11 | Sep 14 | Sep 17 | Sep 20 | Sep 23 | Sep 28 |
| 28°F | Sep 11 | Sep 17 | Sep 21 | Sep 23 | Sep 26 | Sep 29 | Oct 1 | Oct 4 | Oct 9 |
| 24°F | Sep 23 | Sep 27 | Oct 1 | Oct 2 | Oct 5 | Oct 9 | Oct 13 | Oct 16 | Oct 20 |
| 20°F | Oct 1 | Oct 5 | Oct 9 | Oct 14 | Oct 18 | Oct 21 | Oct 24 | Oct 27 | Nov 1 |
| 16°F | Oct 8 | Oct 16 | Oct 21 | Oct 24 | Oct 28 | Nov 1 | Nov 2 | Nov 6 | Nov 12 |
Freeze probabilities 1991–2020 at Columbus, MT, 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 59019 →Compare Columbus with another place →
Weather by month in Columbus
July is the warmest month at Columbus, MT, averaging 85°F by day and 50°F at night; January is the coldest at 37°F and 10°F. A freezing night is all but certain in every month from September to May (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, June still brings one in 34% of years.
Warmth for growing adds up to 1,788 growing degree days a year (base 50°F), fewer than at 62% of the 68 Montana stations. 26% of them (471) have built up by the end of June, and July adds the most, 548. Precipitation totals 15.7 inches a year, most in May (2.8") and least in January (0.6"); May to September bring 55% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 37 | 10 | 0.6 | 100% | 30 | 0 |
| Feb | 40 | 13 | 0.7 | 100% | 27 | 1 |
| Mar | 51 | 21 | 0.9 | 100% | 26 | 3 |
| Apr | 58 | 28 | 2.0 | 100% | 18 | 21 |
| May | 67 | 37 | 2.8 | 99% | 6 | 130 |
| Jun | 76 | 45 | 2.3 | 34% | <1 | 317 |
| Jul | 85 | 50 | 1.2 | 1% | 0 | 548 |
| Aug | 84 | 48 | 0.9 | 10% | <1 | 494 |
| Sep | 74 | 39 | 1.4 | 94% | 3 | 227 |
| Oct | 60 | 29 | 1.5 | 100% | 16 | 45 |
| Nov | 46 | 19 | 0.7 | 100% | 26 | 3 |
| Dec | 37 | 11 | 0.7 | 100% | 30 | 0 |
Monthly normals 1991–2020 at Columbus, MT (3,602 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, Joliet, MT, 15 miles southeast of Columbus and 236 feet higher, has a last frost 2 days later (May 29), a first frost 1 day later (September 15), a season 1 day shorter.
When it snows in Columbus, Montana
The first measurable snow (0.1 inch or more) in Columbus usually arrives around October 19, and the last of the season around April 25. Those are the middle dates across the winters of 1991–2020 at Columbus, MT, 2.9 miles away: half of years saw snow earlier, half later. Snow fell in 89% of those winters. The last 32°F night of spring typically comes 32 days after the last snow.
Planting calendar for 59019
| When | What to do |
|---|---|
| March 18 – April 1 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| April 1 – April 15 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 29 – May 13 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 27 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 59019 is 3 miles from Columbus, MT, which stands at 3,602 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 59019 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°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.