Woodcrest Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Riverside Fire Stn 3. 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 January 9 and the first fall freeze around December 25, a growing season of about 353 days.
- Median at 36°F
- last February 19, first December 6
- Median at 32°F
- last January 9, first December 25
- Median at 28°F
- last December 31, first December 29
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 | Mar 22 | Mar 11 | Mar 4 | Feb 27 | Feb 19 | Feb 10 | Feb 2 | Jan 21 | Jan 8 |
| 32°F | Feb 25 | Feb 6 | Jan 25 | Jan 17 | Jan 9 | Jan 4 | Dec 31 | Dec 25 | Dec 16 |
| 28°F | Jan 16 | Jan 8 | Jan 5 | Jan 1 | Dec 31 | Dec 28 | Dec 25 | Dec 19 | Dec 13 |
| 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 | Nov 15 | Nov 24 | Nov 29 | Dec 2 | Dec 6 | Dec 11 | Dec 15 | Dec 21 | Jan 1 |
| 32°F | Dec 1 | Dec 10 | Dec 15 | Dec 20 | Dec 25 | Dec 30 | Jan 4 | Jan 11 | Jan 27 |
| 28°F | Nov 30 | Dec 13 | Dec 20 | Dec 25 | Dec 29 | Dec 31 | Jan 2 | Jan 7 | Jan 13 |
| 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 | 335 | 322 | 310 | 301 | 293 | 283 | 273 | 263 | 252 |
| 32°F | 365 | 365 | 365 | 360 | 353 | 345 | 338 | 327 | 307 |
| 28°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 363 |
| 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
- 99% of years
- 32°F or colder
- 69% of years
- 28°F or colder
- 11% of years
- 24°F or colder
- 1% 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
- 1,258
- Cooling degree days, base 65°F
- 1,977
- Growing degree days, base 40°F
- 9,844
- Growing degree days, base 45°F
- 8,020
- Growing degree days, base 50°F
- 6,222
- Growing degree days, base 55°F
- 4,545
- Growing degree days, base 60°F
- 3,113
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 270 | 3 | 207 |
| February | 232 | 6 | 199 |
| March | 181 | 15 | 302 |
| April | 85 | 53 | 419 |
| May | 32 | 126 | 560 |
| June | 2 | 274 | 722 |
| July | 0 | 449 | 915 |
| August | 0 | 485 | 950 |
| September | 0 | 372 | 822 |
| October | 23 | 159 | 601 |
| November | 139 | 31 | 343 |
| December | 294 | 2 | 184 |
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 8.2 km from Woodcrest. 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 USC00047470 (Riverside Fire Stn 3). Public domain.