USDA Hardiness Zone 5a
Frost Dates for 59711 — Anaconda, Montana
NOAA 1991–2020 normals from Anaconda, MT (5,230 ft), 3 miles east.
Updated
In Anaconda, the last spring frost (32°F) is around June 1 in half of years and has passed by June 25 in nine years out of ten. The first fall frost comes around September 14, as early as August 31 one year in ten, leaving a typical freeze-free season of 105 days (NOAA, Anaconda, MT).
- Last spring frost
- June 1
- First fall frost
- September 14
- Growing season
- 105 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 6
- Last snow
- May 21
- Winters with snow
- 100%
- Snow per year
- 75.1"
median, 1991–2020
median, 1991–2020
24 of 24 observed
NOAA normal
Frost risk by date in Anaconda
Half of springs at Anaconda, MT see their last 32°F night by June 1; only one in ten is past it by May 14, and one in ten still has one after June 25. Planting tender crops after June 11 leaves a 30% risk of a frost on them, after June 17 20%, and after June 25 10%. The 24 days between the even-odds date and the one-in-ten date is the widest of the 68 Montana stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.
In fall the first 32°F night comes by September 14 in half of years, as early as August 31 one year in ten, and holds off past October 1 one year in ten. A hard freeze of 28°F follows 14 days later, around September 28; in spring the one-in-ten date for 28°F is May 30, 26 days before the 32°F one. The freeze-free season lasts 105 days in a typical year, shorter than at 87% of the 68 Montana stations; it reaches 129 days one year in ten and falls short of 78 one year in ten. On average 201 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between October 31 and April 6.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | May 14 | May 20 | May 25 | May 29 | Jun 1 | Jun 5 | Jun 11 | Jun 17 | Jun 25 |
| 28°F | Apr 29 | May 3 | May 6 | May 10 | May 13 | May 16 | May 19 | May 23 | May 30 |
| 24°F | Apr 17 | Apr 22 | Apr 25 | Apr 29 | May 1 | May 3 | May 6 | May 9 | May 13 |
| 20°F | Apr 2 | Apr 8 | Apr 12 | Apr 16 | Apr 20 | Apr 23 | Apr 27 | Apr 30 | May 4 |
| 16°F | Mar 14 | Mar 21 | Mar 29 | Apr 2 | Apr 6 | Apr 9 | Apr 14 | Apr 19 | Apr 26 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | Aug 31 | Sep 4 | Sep 8 | Sep 11 | Sep 14 | Sep 17 | Sep 21 | Sep 24 | Oct 1 |
| 28°F | Sep 12 | Sep 17 | Sep 22 | Sep 25 | Sep 28 | Oct 1 | Oct 3 | Oct 6 | Oct 12 |
| 24°F | Sep 23 | Sep 29 | Oct 2 | Oct 5 | Oct 7 | Oct 11 | Oct 14 | Oct 18 | Oct 23 |
| 20°F | Oct 3 | Oct 7 | Oct 12 | Oct 16 | Oct 19 | Oct 22 | Oct 26 | Oct 31 | Nov 5 |
| 16°F | Oct 12 | Oct 18 | Oct 24 | Oct 28 | Oct 31 | Nov 2 | Nov 6 | Nov 10 | Nov 15 |
Freeze probabilities 1991–2020 at Anaconda, 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 59711 →Compare Anaconda with another place →
Weather by month in Anaconda
July is the warmest month at Anaconda, MT, averaging 83°F by day and 49°F at night; December is the coldest at 34°F and 15°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). July is the only month with under a 10% chance of a 32°F night. In spring, June still brings one in 50% of years.
Warmth for growing adds up to 1,559 growing degree days a year (base 50°F), fewer than at 84% of the 68 Montana stations. 24% of them (371) have built up by the end of June, and July adds the most, 487. Precipitation totals 15.0 inches a year, most in June (2.2") and least in January (0.6"); May to September bring 53% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 37 | 16 | 0.6 | 100% | 30 | 0 |
| Feb | 39 | 16 | 1.0 | 100% | 27 | 0 |
| Mar | 48 | 23 | 1.2 | 100% | 28 | 1 |
| Apr | 55 | 28 | 1.5 | 100% | 23 | 17 |
| May | 64 | 36 | 2.1 | 99% | 10 | 105 |
| Jun | 73 | 43 | 2.2 | 50% | 2 | 247 |
| Jul | 83 | 49 | 1.3 | 5% | <1 | 487 |
| Aug | 82 | 47 | 1.2 | 10% | <1 | 448 |
| Sep | 72 | 40 | 1.2 | 89% | 5 | 212 |
| Oct | 57 | 31 | 1.0 | 100% | 19 | 39 |
| Nov | 43 | 21 | 1.0 | 100% | 27 | 2 |
| Dec | 34 | 15 | 0.7 | 100% | 30 | 0 |
Monthly normals 1991–2020 at Anaconda, MT (5,230 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, Butte Bert Mooney Airport, MT, 26 miles southeast of Anaconda and 276 feet higher, has a last frost 12 days later (June 13), a first frost 9 days earlier (September 5), a season 22 days shorter.
When it snows in Anaconda, Montana
The first measurable snow (0.1 inch or more) in Anaconda usually arrives around October 6, and the last of the season around May 21. Those are the middle dates across the winters of 1991–2020 at Anaconda, MT, 2.8 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 11 days after the last snow.
Planting calendar for 59711
| When | What to do |
|---|---|
| March 23 – April 6 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| April 6 – April 20 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| May 4 – May 18 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| June 1 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 59711 is 3 miles from Anaconda, MT, which stands at 5,230 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 59711 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.