USDA Hardiness Zone 5a
Frost Dates for 83254 — Montpelier, Idaho
NOAA 1991–2020 normals from Bern, ID (5,964 ft), 3 miles west.
Updated
In Montpelier, the last spring frost (32°F) is around June 17 in half of years and has passed by July 4 in nine years out of ten. The first fall frost comes around September 3, as early as August 18 one year in ten, leaving a typical freeze-free season of 77 days (NOAA, Bern, ID).
- Last spring frost
- June 17
- First fall frost
- September 3
- Growing season
- 77 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 18
- Last snow
- May 9
- Winters with snow
- 100%
- Snow per year
- 90.6"
median, 1991–2020
median, 1991–2020
28 of 28 observed
NOAA normal
Frost risk by date in Montpelier
Half of springs at Bern, ID see their last 32°F night by June 17; only one in ten is past it by May 31, and one in ten still has one after July 4. Planting tender crops after June 25 leaves a 30% risk of a frost on them, after June 30 20%, and after July 4 10%. The 17 days between the even-odds date and the one-in-ten date is narrower than at 54% of the 67 Idaho stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 3 in half of years, as early as August 18 one year in ten, and holds off past September 18 one year in ten. A hard freeze of 28°F follows 13 days later, around September 16; in spring the one-in-ten date for 28°F is June 17, 17 days before the 32°F one. The freeze-free season lasts 77 days in a typical year, the shortest of the 67 Idaho stations; it reaches 102 days one year in ten and falls short of 53 one year in ten. On average 217 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between October 24 and April 6.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | May 31 | Jun 5 | Jun 9 | Jun 14 | Jun 17 | Jun 21 | Jun 25 | Jun 30 | Jul 4 |
| 28°F | May 9 | May 14 | May 18 | May 21 | May 25 | May 30 | Jun 3 | Jun 9 | Jun 17 |
| 24°F | Apr 23 | Apr 28 | May 1 | May 4 | May 7 | May 10 | May 14 | May 18 | May 26 |
| 20°F | Apr 6 | Apr 12 | Apr 15 | Apr 18 | Apr 21 | Apr 25 | Apr 28 | May 2 | May 7 |
| 16°F | Mar 21 | Mar 29 | Apr 1 | Apr 4 | Apr 6 | Apr 9 | Apr 13 | Apr 17 | Apr 23 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | Aug 18 | Aug 24 | Aug 29 | Sep 1 | Sep 3 | Sep 6 | Sep 10 | Sep 13 | Sep 18 |
| 28°F | Sep 1 | Sep 5 | Sep 9 | Sep 13 | Sep 16 | Sep 19 | Sep 23 | Sep 27 | Oct 1 |
| 24°F | Sep 10 | Sep 17 | Sep 22 | Sep 26 | Sep 29 | Oct 2 | Oct 5 | Oct 10 | Oct 15 |
| 20°F | Sep 26 | Oct 1 | Oct 4 | Oct 7 | Oct 11 | Oct 15 | Oct 19 | Oct 22 | Oct 26 |
| 16°F | Oct 6 | Oct 13 | Oct 18 | Oct 21 | Oct 24 | Oct 26 | Oct 30 | Nov 2 | Nov 7 |
Freeze probabilities 1991–2020 at Bern, ID, 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 83254 →Compare Montpelier with another place →
Weather by month in Montpelier
July is the warmest month at Bern, ID, averaging 85°F by day and 46°F at night; January is the coldest at 29°F and 7°F. A freezing night is all but certain in every month from September to May (a 90% chance or more). No month is safe from a 32°F night: even the warmest has at least a 10% chance. In spring, June still brings one in 86% of years and July still brings one in 17% of years.
Warmth for growing adds up to 1,463 growing degree days a year (base 50°F), fewer than at 94% of the 67 Idaho stations. 23% of them (331) have built up by the end of June, and July adds the most, 478. Precipitation totals 18.0 inches a year, most in May (2.3") and least in July (0.7"); May to September bring 37% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 29 | 7 | 1.7 | 100% | 31 | 0 |
| Feb | 32 | 9 | 1.6 | 100% | 28 | 0 |
| Mar | 42 | 18 | 1.5 | 100% | 30 | 0 |
| Apr | 53 | 27 | 1.7 | 100% | 23 | 9 |
| May | 64 | 34 | 2.3 | 100% | 10 | 81 |
| Jun | 75 | 40 | 1.3 | 86% | 3 | 241 |
| Jul | 85 | 46 | 0.7 | 17% | <1 | 478 |
| Aug | 84 | 45 | 1.0 | 38% | 1 | 443 |
| Sep | 74 | 37 | 1.4 | 99% | 8 | 188 |
| Oct | 59 | 27 | 1.7 | 100% | 23 | 23 |
| Nov | 43 | 19 | 1.4 | 100% | 29 | 0 |
| Dec | 30 | 9 | 1.7 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Bern, ID (5,964 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, Grace, ID, 27 miles northwest of Montpelier and 414 feet lower, has a last frost 19 days earlier (May 29), a first frost 14 days later (September 17), a season 34 days longer.
When it snows in Montpelier, Idaho
The first measurable snow (0.1 inch or more) in Montpelier usually arrives around October 18, and the last of the season around May 9. Those are the middle dates across the winters of 1991–2020 at Bern, ID, 3 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 39 days after the last snow.
Planting calendar for 83254
| When | What to do |
|---|---|
| April 8 – April 22 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| April 22 – May 6 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| May 20 – June 3 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| June 17 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by June 11 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by August 20 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 3 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 83254 is 3 miles from Bern, ID, which stands at 5,964 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 83254 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.