Fruitland Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Malheur Branch Exp Stn. A median date has an even chance of a later freeze in spring, or an earlier one in fall.
The last spring freeze typically comes around April 23 and the first fall freeze around October 13, a growing season of about 173 days.
- Median at 36°F
- last May 6, first October 2
- Median at 32°F
- last April 23, first October 13
- Median at 28°F
- last April 6, first October 26
Last freeze in spring
The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.
| Threshold | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 24 | May 16 | May 13 | May 9 | May 6 | May 3 | Apr 30 | Apr 27 | Apr 22 |
| 32°F | May 9 | May 3 | Apr 30 | Apr 27 | Apr 23 | Apr 20 | Apr 17 | Apr 11 | Apr 6 |
| 28°F | Apr 25 | Apr 19 | Apr 14 | Apr 9 | Apr 6 | Apr 2 | Mar 30 | Mar 25 | Mar 15 |
| 24°F | Apr 7 | Apr 1 | Mar 27 | Mar 18 | Mar 12 | Mar 7 | Mar 3 | Feb 27 | Feb 21 |
| 20°F | Mar 13 | Mar 6 | Mar 1 | Feb 26 | Feb 22 | Feb 18 | Feb 13 | Feb 8 | Jan 30 |
| 16°F | Mar 1 | Feb 23 | Feb 17 | Feb 13 | Feb 8 | Feb 3 | Jan 27 | Jan 15 | Jan 5 |
First freeze in fall
The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.
| Threshold | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 20 | Sep 25 | Sep 28 | Sep 30 | Oct 2 | Oct 5 | Oct 8 | Oct 11 | Oct 16 |
| 32°F | Oct 1 | Oct 5 | Oct 8 | Oct 11 | Oct 13 | Oct 16 | Oct 19 | Oct 23 | Oct 29 |
| 28°F | Oct 12 | Oct 17 | Oct 20 | Oct 24 | Oct 26 | Oct 30 | Nov 1 | Nov 6 | Nov 10 |
| 24°F | Oct 24 | Oct 29 | Nov 1 | Nov 4 | Nov 8 | Nov 11 | Nov 15 | Nov 18 | Nov 23 |
| 20°F | Nov 1 | Nov 7 | Nov 11 | Nov 16 | Nov 20 | Nov 23 | Nov 27 | Nov 30 | Dec 6 |
| 16°F | Nov 8 | Nov 15 | Nov 23 | Nov 27 | Dec 1 | Dec 5 | Dec 10 | Dec 19 | Dec 30 |
Growing season length
Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.
| Threshold | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | 167 | 160 | 155 | 151 | 147 | 143 | 138 | 132 | 123 |
| 32°F | 195 | 188 | 182 | 177 | 173 | 169 | 163 | 158 | 151 |
| 28°F | 228 | 219 | 213 | 208 | 204 | 198 | 193 | 187 | 178 |
| 24°F | 265 | 255 | 248 | 242 | 237 | 231 | 225 | 217 | 209 |
| 20°F | 298 | 288 | 281 | 274 | 269 | 263 | 256 | 250 | 242 |
| 16°F | 332 | 320 | 312 | 305 | 297 | 291 | 283 | 275 | 264 |
How often it gets that cold
The share of years with at least one night at or below each temperature.
- 36°F or colder
- 100% of years
- 32°F or colder
- 100% of years
- 28°F or colder
- 100% of years
- 24°F or colder
- 100% of years
- 20°F or colder
- 100% of years
- 16°F or colder
- 99% of years
Degree days
A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.
- Heating degree days, base 65°F
- 5,556
- Cooling degree days, base 65°F
- 917
- Growing degree days, base 40°F
- 5,378
- Growing degree days, base 45°F
- 4,156
- Growing degree days, base 50°F
- 3,107
- Growing degree days, base 55°F
- 2,230
- Growing degree days, base 60°F
- 1,502
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 1,074 | 0 | 0 |
| February | 816 | 0 | 1 |
| March | 631 | 0 | 19 |
| April | 416 | 2 | 98 |
| May | 186 | 42 | 328 |
| June | 57 | 136 | 530 |
| July | 5 | 358 | 818 |
| August | 9 | 297 | 753 |
| September | 92 | 79 | 438 |
| October | 416 | 3 | 118 |
| November | 787 | 0 | 4 |
| December | 1,066 | 0 | 0 |
What this means
NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.
The station is 9.2 km from Fruitland. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.
More
Sources
NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00355160 (Malheur Branch Exp Stn). Public domain.