USDA Hardiness Zone 5a
Frost Dates for 59043 — Lame Deer, Montana
NOAA 1991–2020 normals from Busby, MT (3,430 ft), 16 miles west.
Updated
In Lame Deer, the last spring frost (32°F) is around May 23 in half of years and has passed by June 7 in nine years out of ten. The first fall frost comes around September 15, as early as September 1 one year in ten, leaving a typical freeze-free season of 113 days (NOAA, Busby, MT).
- Last spring frost
- May 23
- First fall frost
- September 15
- Growing season
- 113 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 21
- Last snow
- April 23
- Winters with snow
- 100%
- Snow per year
- 52.3"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Lame Deer
Half of springs at Busby, MT see their last 32°F night by May 23; only one in ten is past it by May 12, and one in ten still has one after June 7. Planting tender crops after May 29 leaves a 30% risk of a frost on them, after June 1 20%, and after June 7 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 53% of the 68 Montana 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 September 1 one year in ten, and holds off past October 1 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 24, 14 days before the 32°F one. The freeze-free season lasts 113 days in a typical year, shorter than at 74% of the 68 Montana stations; it reaches 131 days one year in ten and falls short of 93 one year in ten. On average 193 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 8, and return around September 4. Severe cold of 16°F or below comes every winter, usually between October 26 and April 4.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 24 | May 29 | Jun 2 | Jun 5 | Jun 8 | Jun 13 | Jun 16 | Jun 22 | Jul 2 |
| 32°F | May 12 | May 15 | May 18 | May 21 | May 23 | May 26 | May 29 | Jun 1 | Jun 7 |
| 28°F | Apr 30 | May 3 | May 6 | May 9 | May 11 | May 13 | May 16 | May 19 | May 24 |
| 24°F | Apr 14 | Apr 20 | Apr 23 | Apr 26 | Apr 29 | Apr 30 | May 2 | May 6 | May 11 |
| 20°F | Apr 1 | Apr 5 | Apr 10 | Apr 14 | Apr 17 | Apr 20 | Apr 24 | Apr 28 | May 2 |
| 16°F | Mar 15 | Mar 23 | Mar 29 | Apr 1 | Apr 4 | Apr 8 | Apr 12 | Apr 17 | Apr 24 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 20 | Aug 26 | Aug 30 | Sep 1 | Sep 4 | Sep 6 | Sep 9 | Sep 13 | Sep 18 |
| 32°F | Sep 1 | Sep 5 | Sep 9 | Sep 12 | Sep 15 | Sep 18 | Sep 21 | Sep 25 | Oct 1 |
| 28°F | Sep 11 | Sep 17 | Sep 21 | Sep 24 | Sep 27 | Oct 1 | Oct 3 | Oct 6 | Oct 11 |
| 24°F | Sep 23 | Sep 28 | Oct 1 | Oct 4 | Oct 6 | Oct 9 | Oct 13 | Oct 16 | Oct 21 |
| 20°F | Oct 1 | Oct 6 | Oct 10 | Oct 14 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Oct 31 |
| 16°F | Oct 9 | Oct 15 | Oct 19 | Oct 23 | Oct 26 | Oct 29 | Nov 1 | Nov 4 | Nov 8 |
Freeze probabilities 1991–2020 at Busby, 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 59043 →Compare Lame Deer with another place →
Weather by month in Lame Deer
July is the warmest month at Busby, MT, averaging 88°F by day and 53°F at night; January is the coldest at 34°F and 9°F. A freezing night is all but certain in every month from October 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 23% of years.
Warmth for growing adds up to 2,154 growing degree days a year (base 50°F), more than at 76% of the 68 Montana stations. 27% of them (579) have built up by the end of June, and July adds the most, 638. Precipitation totals 15.8 inches a year, most in May (2.7") and least in December (0.6"); May to September bring 56% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 34 | 9 | 0.7 | 100% | 31 | 0 |
| Feb | 37 | 11 | 0.7 | 100% | 28 | 0 |
| Mar | 49 | 21 | 1.0 | 100% | 28 | 5 |
| Apr | 59 | 30 | 1.7 | 100% | 19 | 32 |
| May | 68 | 39 | 2.7 | 100% | 7 | 159 |
| Jun | 78 | 47 | 2.1 | 23% | <1 | 384 |
| Jul | 88 | 53 | 1.4 | 0% | 0 | 638 |
| Aug | 88 | 51 | 1.0 | 9% | <1 | 592 |
| Sep | 77 | 41 | 1.6 | 87% | 4 | 289 |
| Oct | 61 | 30 | 1.5 | 100% | 18 | 53 |
| Nov | 46 | 19 | 0.8 | 100% | 28 | 3 |
| Dec | 36 | 10 | 0.6 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Busby, MT (3,430 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, Colstrip, MT, 21 miles north of Lame Deer and 212 feet lower, has a last frost 8 days earlier (May 15), a first frost 15 days later (September 30), a season 25 days longer.
When it snows in Lame Deer, Montana
The first measurable snow (0.1 inch or more) in Lame Deer usually arrives around October 21, and the last of the season around April 23. Those are the middle dates across the winters of 1991–2020 at Busby, MT, 15.9 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 30 days after the last snow.
Planting calendar for 59043
| When | What to do |
|---|---|
| March 14 – March 28 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 28 – April 11 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 25 – May 9 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 23 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 59043 is 16 miles from Busby, MT, which stands at 3,430 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 59043 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.