USDA Hardiness Zone 6b
Frost Dates for 97623 — Bonanza, Oregon
NOAA 1991–2020 normals from Gerber Dam, OR (4,870 ft), 10 miles east.
Updated
In Bonanza, the last spring frost (32°F) is around May 31 in half of years and has passed by June 17 in nine years out of ten. The first fall frost comes around September 21, as early as September 6 one year in ten, leaving a typical freeze-free season of 114 days (NOAA, Gerber Dam, OR).
- Last spring frost
- May 31
- First fall frost
- September 21
- Growing season
- 114 days
- Hardiness zone
- 6b
50% probability
50% probability
freeze-free, 50%
-5 to 0°F (-20.6 to -17.8°C) coldest night
- First snow
- November 22
- Last snow
- April 13
- Winters with snow
- 100%
- Snow per year
- 22.8"
median, 1991–2020
median, 1991–2020
21 of 21 observed
NOAA normal
Frost risk by date in Bonanza
Half of springs at Gerber Dam, OR see their last 32°F night by May 31; only one in ten is past it by May 7, and one in ten still has one after June 17. Planting tender crops after June 6 leaves a 30% risk of a frost on them, after June 11 20%, and after June 17 10%. The 17 days between the even-odds date and the one-in-ten date is narrower than at 83% of the 103 Oregon stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 21 in half of years, as early as September 6 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 4; in spring the one-in-ten date for 28°F is May 30, 18 days before the 32°F one. The freeze-free season lasts 114 days in a typical year, shorter than at 88% of the 103 Oregon stations; it reaches 141 days one year in ten and falls short of 89 one year in ten. On average 191 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 14 days longer, to about June 14, and return around September 10. Severe cold of 16°F or below comes every winter, usually between November 22 and March 3.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 29 | Jun 4 | Jun 8 | Jun 12 | Jun 14 | Jun 18 | Jun 21 | Jun 25 | Jun 30 |
| 32°F | May 7 | May 14 | May 20 | May 25 | May 31 | Jun 3 | Jun 6 | Jun 11 | Jun 17 |
| 28°F | Apr 20 | Apr 25 | Apr 30 | May 2 | May 5 | May 9 | May 14 | May 19 | May 30 |
| 24°F | Mar 31 | Apr 5 | Apr 9 | Apr 13 | Apr 17 | Apr 22 | Apr 25 | Apr 30 | May 7 |
| 20°F | Mar 1 | Mar 9 | Mar 16 | Mar 21 | Mar 25 | Mar 31 | Apr 4 | Apr 8 | Apr 17 |
| 16°F | Feb 4 | Feb 15 | Feb 22 | Feb 28 | Mar 3 | Mar 7 | Mar 12 | Mar 19 | Mar 28 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 25 | Sep 1 | Sep 4 | Sep 8 | Sep 10 | Sep 13 | Sep 15 | Sep 18 | Sep 21 |
| 32°F | Sep 6 | Sep 11 | Sep 15 | Sep 18 | Sep 21 | Sep 23 | Sep 26 | Sep 29 | Oct 4 |
| 28°F | Sep 19 | Sep 25 | Sep 28 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 19 |
| 24°F | Oct 4 | Oct 8 | Oct 12 | Oct 16 | Oct 20 | Oct 24 | Oct 29 | Nov 2 | Nov 7 |
| 20°F | Oct 22 | Oct 28 | Nov 1 | Nov 4 | Nov 8 | Nov 11 | Nov 16 | Nov 21 | Nov 29 |
| 16°F | Nov 2 | Nov 8 | Nov 12 | Nov 17 | Nov 22 | Nov 26 | Dec 1 | Dec 5 | Dec 13 |
Freeze probabilities 1991–2020 at Gerber Dam, OR, 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 97623 →Compare Bonanza with another place →
Compared with the next station
The nearest other station, Tulelake, CA, 18 miles southwest of Bonanza and 832 feet lower, has a last frost 6 days later (June 6), a first frost 7 days earlier (September 14), a season 17 days shorter.
When it snows in Bonanza, Oregon
The first measurable snow (0.1 inch or more) in Bonanza usually arrives around November 22, and the last of the season around April 13. Those are the middle dates across the winters of 1991–2020 at Tulelake, CA, 18.2 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 48 days after the last snow.
Planting calendar for 97623
| When | What to do |
|---|---|
| March 22 – April 5 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| April 5 – April 19 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| May 3 – May 17 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 31 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by June 29 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 7 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 21 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 97623 is 10 miles from Gerber Dam, OR, which stands at 4,870 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 97623 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°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.