Port Orford Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Port Orford #2. 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 February 17 and the first fall freeze around December 3, a growing season of about 292 days.
- Median at 36°F
- last March 30, first November 11
- Median at 32°F
- last February 17, first December 3
- Median at 28°F
- last January 6, first December 22
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 | Apr 28 | Apr 17 | Apr 10 | Apr 3 | Mar 30 | Mar 25 | Mar 17 | Mar 6 | Feb 22 |
| 32°F | Mar 19 | Mar 7 | Feb 28 | Feb 23 | Feb 17 | Feb 8 | Jan 31 | Jan 16 | Dec 28 |
| 28°F | Feb 22 | Feb 12 | Jan 30 | Jan 15 | Jan 6 | Dec 31 | Dec 24 | Dec 15 | Dec 4 |
| 24°F | – | – | – | – | – | – | – | – | – |
| 20°F | – | – | – | – | – | – | – | – | – |
| 16°F | – | – | – | – | – | – | – | – | – |
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 | Oct 21 | Oct 28 | Nov 2 | Nov 7 | Nov 11 | Nov 15 | Nov 20 | Nov 26 | Dec 4 |
| 32°F | Nov 8 | Nov 16 | Nov 23 | Nov 29 | Dec 3 | Dec 8 | Dec 17 | Dec 26 | Jan 11 |
| 28°F | Nov 27 | Dec 4 | Dec 9 | Dec 15 | Dec 22 | Dec 30 | Jan 5 | Jan 22 | Feb 16 |
| 24°F | – | – | – | – | – | – | – | – | – |
| 20°F | – | – | – | – | – | – | – | – | – |
| 16°F | – | – | – | – | – | – | – | – | – |
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 | 265 | 254 | 245 | 238 | 229 | 221 | 214 | 205 | 193 |
| 32°F | 340 | 326 | 312 | 302 | 292 | 284 | 276 | 266 | 253 |
| 28°F | 365 | 365 | 365 | 365 | 357 | 346 | 337 | 329 | 313 |
| 24°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 |
| 20°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 |
| 16°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 |
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
- 96% of years
- 28°F or colder
- 52% of years
- 24°F or colder
- 5% of years
- 20°F or colder
- 0% of years
- 16°F or colder
- 0% 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
- 4,218
- Cooling degree days, base 65°F
- 11
- Growing degree days, base 40°F
- 4,928
- Growing degree days, base 45°F
- 3,186
- Growing degree days, base 50°F
- 1,718
- Growing degree days, base 55°F
- 709
- Growing degree days, base 60°F
- 162
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 527 | 0 | 34 |
| February | 473 | 0 | 27 |
| March | 501 | 0 | 33 |
| April | 435 | 0 | 51 |
| May | 335 | 1 | 136 |
| June | 229 | 1 | 222 |
| July | 136 | 3 | 332 |
| August | 128 | 3 | 340 |
| September | 176 | 3 | 278 |
| October | 301 | 1 | 173 |
| November | 438 | 0 | 61 |
| December | 539 | 0 | 31 |
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 0.7 km from Port Orford. 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 USC00356784 (Port Orford #2). Public domain.