San Pasqual Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for San Pasqual Animal Pk. 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 2 and the first fall freeze around December 7, a growing season of about 309 days.
- Median at 36°F
- last March 5, first November 23
- Median at 32°F
- last February 2, first December 7
- Median at 28°F
- last January 5, first December 19
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 5 | Mar 28 | Mar 20 | Mar 12 | Mar 5 | Feb 28 | Feb 23 | Feb 13 | Jan 30 |
| 32°F | Mar 4 | Feb 25 | Feb 17 | Feb 8 | Feb 2 | Jan 26 | Jan 17 | Jan 9 | Dec 31 |
| 28°F | Feb 7 | Jan 30 | Jan 18 | Jan 11 | Jan 5 | Dec 31 | Dec 29 | Dec 22 | Dec 15 |
| 24°F | Jan 17 | Jan 9 | Jan 2 | Dec 30 | Dec 28 | Dec 25 | Dec 21 | Dec 17 | Dec 9 |
| 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 6 | Nov 12 | Nov 16 | Nov 20 | Nov 23 | Nov 28 | Dec 1 | Dec 4 | Dec 11 |
| 32°F | Nov 22 | Nov 28 | Dec 1 | Dec 4 | Dec 7 | Dec 13 | Dec 17 | Dec 24 | Jan 1 |
| 28°F | Dec 2 | Dec 6 | Dec 10 | Dec 15 | Dec 19 | Dec 24 | Dec 30 | Jan 3 | Jan 14 |
| 24°F | Dec 5 | Dec 10 | Dec 14 | Dec 19 | Dec 24 | Dec 26 | Dec 29 | Jan 2 | Jan 10 |
| 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 | 300 | 285 | 276 | 268 | 262 | 255 | 247 | 239 | 229 |
| 32°F | 344 | 334 | 326 | 317 | 309 | 302 | 294 | 285 | 275 |
| 28°F | 365 | 365 | 362 | 354 | 348 | 343 | 338 | 330 | 317 |
| 24°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 360 | 347 |
| 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
- 98% of years
- 28°F or colder
- 73% of years
- 24°F or colder
- 24% of years
- 20°F or colder
- 2% 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
- 1,327
- Cooling degree days, base 65°F
- 1,356
- Growing degree days, base 40°F
- 9,154
- Growing degree days, base 45°F
- 7,330
- Growing degree days, base 50°F
- 5,528
- Growing degree days, base 55°F
- 3,846
- Growing degree days, base 60°F
- 2,434
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 284 | 3 | 192 |
| February | 223 | 3 | 203 |
| March | 173 | 9 | 301 |
| April | 95 | 32 | 387 |
| May | 42 | 75 | 498 |
| June | 5 | 165 | 611 |
| July | 0 | 298 | 763 |
| August | 0 | 358 | 823 |
| September | 1 | 283 | 732 |
| October | 28 | 108 | 546 |
| November | 147 | 21 | 325 |
| December | 329 | 1 | 149 |
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 4.1 km from San Pasqual. 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 USC00047874 (San Pasqual Animal Pk). Public domain.