USDA Hardiness Zone 4b
Frost Dates for 59722 — Deer Lodge, Montana
NOAA 1991–2020 normals from Elliston, MT (5,080 ft), 19 miles northeast.
Updated
In Deer Lodge, the last spring frost (32°F) is around June 9 in half of years and has passed by June 26 in nine years out of ten. The first fall frost comes around September 8, as early as August 26 one year in ten, leaving a typical freeze-free season of 91 days (NOAA, Elliston, MT).
- Last spring frost
- June 9
- First fall frost
- September 8
- Growing season
- 91 days
- Hardiness zone
- 4b
50% probability
50% probability
freeze-free, 50%
-25 to -20°F (-31.7 to -28.9°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 Deer Lodge
Half of springs at Elliston, MT see their last 32°F night by June 9; only one in ten is past it by May 23, and one in ten still has one after June 26. Planting tender crops after June 16 leaves a 30% risk of a frost on them, after June 20 20%, and after June 26 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 62% of the 68 Montana stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 8 in half of years, as early as August 26 one year in ten, and holds off past September 21 one year in ten. A hard freeze of 28°F follows 12 days later, around September 20; in spring the one-in-ten date for 28°F is June 3, 23 days before the 32°F one. The freeze-free season lasts 91 days in a typical year, shorter than at 91% of the 68 Montana stations; it reaches 111 days one year in ten and falls short of 68 one year in ten. On average 219 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between October 22 and April 11.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | May 23 | May 30 | Jun 3 | Jun 6 | Jun 9 | Jun 12 | Jun 16 | Jun 20 | Jun 26 |
| 28°F | May 2 | May 7 | May 10 | May 13 | May 16 | May 20 | May 23 | May 27 | Jun 3 |
| 24°F | Apr 21 | Apr 25 | Apr 28 | Apr 30 | May 2 | May 4 | May 7 | May 10 | May 15 |
| 20°F | Apr 10 | Apr 13 | Apr 17 | Apr 20 | Apr 22 | Apr 25 | Apr 28 | Apr 30 | May 5 |
| 16°F | Mar 25 | Apr 1 | Apr 4 | Apr 8 | Apr 11 | Apr 15 | Apr 19 | Apr 23 | Apr 28 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | Aug 26 | Aug 31 | Sep 3 | Sep 5 | Sep 8 | Sep 11 | Sep 13 | Sep 17 | Sep 21 |
| 28°F | Sep 6 | Sep 12 | Sep 15 | Sep 18 | Sep 20 | Sep 22 | Sep 25 | Sep 29 | Oct 3 |
| 24°F | Sep 18 | Sep 23 | Sep 26 | Sep 29 | Oct 1 | Oct 3 | Oct 7 | Oct 11 | Oct 16 |
| 20°F | Sep 26 | Oct 1 | Oct 4 | Oct 7 | Oct 11 | Oct 15 | Oct 19 | Oct 23 | Oct 28 |
| 16°F | Oct 2 | Oct 8 | Oct 13 | Oct 17 | Oct 22 | Oct 25 | Oct 28 | Nov 1 | Nov 5 |
Freeze probabilities 1991–2020 at Elliston, 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 59722 →Compare Deer Lodge with another place →
Weather by month in Deer Lodge
July is the warmest month at Elliston, MT, averaging 81°F by day and 46°F at night; December is the coldest at 31°F and 10°F. A freezing night is all but certain in every month from September 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 75% of years.
Warmth for growing adds up to 1,225 growing degree days a year (base 50°F), fewer than at 94% of the 68 Montana stations. 21% of them (253) have built up by the end of June, and July adds the most, 419.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 33 | 11 | 100% | 30 | 0 |
| Feb | 33 | 12 | 100% | 28 | 0 |
| Mar | 43 | 19 | 100% | 30 | 0 |
| Apr | 51 | 26 | 100% | 26 | 5 |
| May | 60 | 35 | 100% | 12 | 71 |
| Jun | 69 | 41 | 75% | 2 | 177 |
| Jul | 81 | 46 | 5% | <1 | 419 |
| Aug | 80 | 44 | 20% | 1 | 385 |
| Sep | 69 | 36 | 99% | 8 | 150 |
| Oct | 53 | 27 | 100% | 24 | 18 |
| Nov | 39 | 17 | 100% | 29 | 0 |
| Dec | 31 | 10 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Elliston, MT (5,080 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, Anaconda, MT, 20 miles southwest of Deer Lodge and 150 feet higher, has a last frost 8 days earlier (June 1), a first frost 6 days later (September 14), a season 14 days longer.
When it snows in Deer Lodge, Montana
The first measurable snow (0.1 inch or more) in Deer Lodge 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, 20.4 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 19 days after the last snow.
Planting calendar for 59722
| When | What to do |
|---|---|
| March 31 – April 14 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| April 14 – April 28 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| May 12 – May 26 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| June 9 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by June 16 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by August 25 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 8 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 59722 is 19 miles from Elliston, MT, which stands at 5,080 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 59722 in zone 4b, the band where the coldest night of the year averaged -25 to -20°F (-31.7 to -28.9°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.