USDA Hardiness Zone 5a
Frost Dates for 83448 — Sugar City, Idaho
NOAA 1991–2020 normals from Sugar City, ID (4,925 ft), 2 miles northwest.
Updated
In Sugar City, the last spring frost (32°F) is around May 29 in half of years and has passed by June 18 in nine years out of ten. The first fall frost comes around September 13, as early as August 30 one year in ten, leaving a typical freeze-free season of 106 days (NOAA, Sugar City, ID).
- Last spring frost
- May 29
- First fall frost
- September 13
- Growing season
- 106 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
- November 7
- Last snow
- April 3
- Winters with snow
- 100%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
24 of 24 observed
NOAA normal
Frost risk by date in Sugar City
Half of springs at Sugar City, ID see their last 32°F night by May 29; only one in ten is past it by May 12, and one in ten still has one after June 18. Planting tender crops after June 5 leaves a 30% risk of a frost on them, after June 10 20%, and after June 18 10%. The 20 days between the even-odds date and the one-in-ten date is wider than at 69% of the 67 Idaho stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 13 in half of years, as early as August 30 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 25; in spring the one-in-ten date for 28°F is May 27, 22 days before the 32°F one. The freeze-free season lasts 106 days in a typical year, shorter than at 91% of the 67 Idaho stations; it reaches 130 days one year in ten and falls short of 83 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 19 days longer, to about June 17, and return around September 2. Severe cold of 16°F or below comes every winter, usually between November 4 and March 24.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 2 | Jun 6 | Jun 9 | Jun 13 | Jun 17 | Jun 20 | Jun 23 | Jun 28 | Jul 2 |
| 32°F | May 12 | May 17 | May 21 | May 25 | May 29 | Jun 1 | Jun 5 | Jun 10 | Jun 18 |
| 28°F | Apr 27 | May 1 | May 4 | May 7 | May 9 | May 12 | May 15 | May 19 | May 27 |
| 24°F | Apr 7 | Apr 13 | Apr 18 | Apr 22 | Apr 26 | Apr 29 | May 2 | May 5 | May 9 |
| 20°F | Mar 19 | Mar 28 | Apr 1 | Apr 5 | Apr 10 | Apr 14 | Apr 18 | Apr 24 | Apr 29 |
| 16°F | Mar 6 | Mar 11 | Mar 14 | Mar 19 | Mar 24 | Mar 30 | Apr 2 | Apr 7 | Apr 15 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 18 | Aug 25 | Aug 28 | Aug 31 | Sep 2 | Sep 4 | Sep 7 | Sep 10 | Sep 15 |
| 32°F | Aug 30 | Sep 3 | Sep 6 | Sep 9 | Sep 13 | Sep 16 | Sep 19 | Sep 23 | Oct 1 |
| 28°F | Sep 7 | Sep 14 | Sep 18 | Sep 22 | Sep 25 | Sep 29 | Oct 3 | Oct 7 | Oct 13 |
| 24°F | Sep 20 | Sep 26 | Oct 1 | Oct 5 | Oct 8 | Oct 13 | Oct 17 | Oct 21 | Oct 28 |
| 20°F | Oct 1 | Oct 9 | Oct 16 | Oct 19 | Oct 23 | Oct 27 | Oct 30 | Nov 3 | Nov 11 |
| 16°F | Oct 19 | Oct 24 | Oct 28 | Nov 1 | Nov 4 | Nov 9 | Nov 13 | Nov 19 | Nov 24 |
Freeze probabilities 1991–2020 at Sugar City, 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 83448 →Compare Sugar City with another place →
Weather by month in Sugar City
July is the warmest month at Sugar City, ID, averaging 83°F by day and 48°F at night; January is the coldest at 29°F and 9°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 43% of years.
Warmth for growing adds up to 1,550 growing degree days a year (base 50°F), fewer than at 90% of the 67 Idaho stations. 26% of them (403) have built up by the end of June, and July adds the most, 467.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 29 | 9 | 100% | 31 | 0 |
| Feb | 34 | 12 | 100% | 26 | 0 |
| Mar | 46 | 23 | 100% | 26 | 1 |
| Apr | 57 | 30 | 100% | 19 | 15 |
| May | 67 | 37 | 99% | 8 | 115 |
| Jun | 75 | 43 | 43% | 1 | 272 |
| Jul | 83 | 48 | 1% | <1 | 467 |
| Aug | 84 | 46 | 13% | <1 | 454 |
| Sep | 74 | 38 | 88% | 6 | 194 |
| Oct | 59 | 29 | 100% | 20 | 32 |
| Nov | 43 | 21 | 100% | 27 | 1 |
| Dec | 30 | 11 | 100% | 30 | 0 |
Monthly normals 1991–2020 at Sugar City, ID (4,925 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, Rexburg Byu Idaho, ID, 5 miles southwest of Sugar City, has a last frost 17 days earlier (May 12), a first frost 11 days later (September 24), a season 26 days longer.
When it snows in Sugar City, Idaho
The first measurable snow (0.1 inch or more) in Sugar City usually arrives around November 7, and the last of the season around April 3. Those are the middle dates across the winters of 1991–2020 at Saint Anthony, ID, 6.5 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 56 days after the last snow.
Planting calendar for 83448
| When | What to do |
|---|---|
| March 20 – April 3 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| April 3 – April 17 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| May 1 – May 15 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 29 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by June 21 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by August 30 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 13 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 83448 is 2 miles from Sugar City, ID, which stands at 4,925 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 83448 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.