Eureka Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Eureka WFO Woodley Island. 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 22 and the first fall freeze around December 7, a growing season of about 293 days.
- Median at 36°F
- last April 1, first November 12
- Median at 32°F
- last February 22, first December 7
- Median at 28°F
- last January 3, first December 25
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 22 | Apr 14 | Apr 9 | Apr 4 | Apr 1 | Mar 28 | Mar 21 | Mar 13 | Mar 1 |
| 32°F | Mar 23 | Mar 14 | Mar 4 | Feb 28 | Feb 22 | Feb 13 | Feb 2 | Jan 18 | Dec 31 |
| 28°F | Feb 8 | Jan 28 | Jan 19 | Jan 11 | Jan 3 | Dec 31 | Dec 27 | Dec 19 | Dec 11 |
| 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 25 | Nov 1 | Nov 4 | Nov 8 | Nov 12 | Nov 16 | Nov 22 | Nov 27 | Dec 4 |
| 32°F | Nov 15 | Nov 21 | Nov 28 | Dec 2 | Dec 7 | Dec 11 | Dec 17 | Dec 27 | Jan 11 |
| 28°F | Dec 3 | Dec 9 | Dec 13 | Dec 20 | Dec 25 | Dec 30 | Jan 4 | Jan 15 | Jan 29 |
| 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 | 262 | 248 | 238 | 230 | 223 | 217 | 211 | 204 | 196 |
| 32°F | 343 | 328 | 317 | 306 | 293 | 283 | 274 | 265 | 251 |
| 28°F | 365 | 365 | 365 | 365 | 365 | 359 | 349 | 339 | 329 |
| 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
- 97% of years
- 28°F or colder
- 48% 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
- 4,506
- Cooling degree days, base 65°F
- 2
- Growing degree days, base 40°F
- 4,629
- Growing degree days, base 45°F
- 2,885
- Growing degree days, base 50°F
- 1,415
- Growing degree days, base 55°F
- 428
- Growing degree days, base 60°F
- 47
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 529 | 0 | 34 |
| February | 466 | 0 | 32 |
| March | 488 | 0 | 39 |
| April | 426 | 0 | 53 |
| May | 352 | 0 | 118 |
| June | 270 | 0 | 180 |
| July | 225 | 0 | 240 |
| August | 202 | 1 | 264 |
| September | 235 | 1 | 216 |
| October | 331 | 0 | 142 |
| November | 435 | 0 | 65 |
| December | 547 | 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 0.9 km from Eureka. 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 USW00024213 (Eureka WFO Woodley Island). Public domain.