USDA Hardiness Zone 5a
Frost Dates for 83611 — Cascade, Idaho
NOAA 1991–2020 normals from Cascade 1 NW, ID (4,896 ft), 5 miles northwest.
Updated
In Cascade, the last spring frost (32°F) is around May 30 in half of years and has passed by June 21 in nine years out of ten. The first fall frost comes around September 19, as early as September 3 one year in ten, leaving a typical freeze-free season of 110 days (NOAA, Cascade 1 NW, ID).
- Last spring frost
- May 30
- First fall frost
- September 19
- Growing season
- 110 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 5
- Last snow
- April 21
- Winters with snow
- 100%
- Snow per year
- 86.3"
median, 1991–2020
median, 1991–2020
27 of 27 observed
NOAA normal
Frost risk by date in Cascade
Half of springs at Cascade 1 NW, ID see their last 32°F night by May 30; only one in ten is past it by May 10, and one in ten still has one after June 21. Planting tender crops after June 8 leaves a 30% risk of a frost on them, after June 14 20%, and after June 21 10%. The 22 days between the even-odds date and the one-in-ten date is wider than at 84% of the 67 Idaho 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 19 in half of years, as early as September 3 one year in ten, and holds off past October 4 one year in ten. A hard freeze of 28°F follows 13 days later, around October 2; in spring the one-in-ten date for 28°F is May 28, 24 days before the 32°F one. The freeze-free season lasts 110 days in a typical year, shorter than at 90% of the 67 Idaho stations; it reaches 136 days one year in ten and falls short of 81 one year in ten. On average 225 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between November 12 and March 23.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | May 10 | May 15 | May 19 | May 24 | May 30 | Jun 3 | Jun 8 | Jun 14 | Jun 21 |
| 28°F | Apr 21 | Apr 27 | May 1 | May 3 | May 6 | May 10 | May 13 | May 18 | May 28 |
| 24°F | Apr 4 | Apr 9 | Apr 12 | Apr 16 | Apr 19 | Apr 23 | Apr 27 | Apr 30 | May 6 |
| 20°F | Mar 18 | Mar 23 | Mar 29 | Apr 1 | Apr 4 | Apr 7 | Apr 10 | Apr 14 | Apr 21 |
| 16°F | Mar 5 | Mar 11 | Mar 15 | Mar 19 | Mar 23 | Mar 27 | Mar 31 | Apr 4 | Apr 10 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | Sep 3 | Sep 7 | Sep 12 | Sep 15 | Sep 19 | Sep 24 | Sep 27 | Oct 1 | Oct 4 |
| 28°F | Sep 15 | Sep 22 | Sep 27 | Sep 30 | Oct 2 | Oct 5 | Oct 9 | Oct 13 | Oct 18 |
| 24°F | Sep 30 | Oct 4 | Oct 8 | Oct 12 | Oct 16 | Oct 20 | Oct 23 | Oct 28 | Nov 3 |
| 20°F | Oct 13 | Oct 19 | Oct 23 | Oct 26 | Oct 30 | Nov 2 | Nov 6 | Nov 11 | Nov 18 |
| 16°F | Oct 25 | Oct 30 | Nov 3 | Nov 8 | Nov 12 | Nov 16 | Nov 20 | Nov 23 | Nov 28 |
Freeze probabilities 1991–2020 at Cascade 1 NW, 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 83611 →Compare Cascade with another place →
Weather by month in Cascade
July is the warmest month at Cascade 1 NW, ID, averaging 82°F by day and 48°F at night; January is the coldest at 32°F and 15°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 44% of years.
Warmth for growing adds up to 1,489 growing degree days a year (base 50°F), fewer than at 91% of the 67 Idaho stations. 22% of them (325) have built up by the end of June, and July adds the most, 474. Precipitation totals 23.8 inches a year, most in December (3.5") and least in August (0.4"); May to September bring 24% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 32 | 15 | 3.0 | 100% | 31 | 0 |
| Feb | 37 | 17 | 2.5 | 100% | 27 | 0 |
| Mar | 45 | 24 | 2.6 | 100% | 29 | 0 |
| Apr | 53 | 30 | 2.1 | 100% | 26 | 10 |
| May | 63 | 37 | 2.1 | 97% | 14 | 92 |
| Jun | 70 | 43 | 1.8 | 44% | 5 | 223 |
| Jul | 82 | 48 | 0.5 | 4% | 1 | 474 |
| Aug | 82 | 47 | 0.4 | 5% | 1 | 446 |
| Sep | 73 | 40 | 1.0 | 78% | 10 | 209 |
| Oct | 58 | 31 | 1.7 | 100% | 23 | 35 |
| Nov | 42 | 25 | 2.6 | 100% | 28 | 0 |
| Dec | 32 | 16 | 3.5 | 100% | 30 | 0 |
Monthly normals 1991–2020 at Cascade 1 NW, ID (4,896 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, Garden Valley, ID, 26 miles south of Cascade and 1,796 feet lower, has a last frost 2 days later (June 1), a first frost 9 days earlier (September 10), a season 8 days shorter.
When it snows in Cascade, Idaho
The first measurable snow (0.1 inch or more) in Cascade usually arrives around November 5, and the last of the season around April 21. Those are the middle dates across the winters of 1991–2020 at Cascade 1 NW, ID, 4.9 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 39 days after the last snow.
Planting calendar for 83611
| When | What to do |
|---|---|
| March 21 – April 4 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| April 4 – April 18 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| May 2 – May 16 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 30 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by June 27 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 5 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 19 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 83611 is 5 miles from Cascade 1 NW, ID, which stands at 4,896 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 83611 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.