Solano County Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Fairfield. 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 15 and the first fall freeze around December 14, a growing season of about 336 days.
- Median at 36°F
- last February 25, first December 1
- Median at 32°F
- last January 15, first December 14
- Median at 28°F
- last December 31, first December 24
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 4 | Mar 24 | Mar 11 | Mar 3 | Feb 25 | Feb 17 | Feb 9 | Feb 2 | Jan 23 |
| 32°F | Feb 16 | Feb 2 | Jan 28 | Jan 21 | Jan 15 | Jan 9 | Jan 3 | Dec 29 | Dec 22 |
| 28°F | Jan 19 | Jan 12 | Jan 6 | Jan 3 | Dec 31 | Dec 29 | Dec 24 | Dec 20 | 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 13 | Nov 19 | Nov 23 | Nov 27 | Dec 1 | Dec 3 | Dec 6 | Dec 12 | Dec 21 |
| 32°F | Nov 29 | Dec 2 | Dec 7 | Dec 11 | Dec 14 | Dec 19 | Dec 25 | Jan 1 | Jan 9 |
| 28°F | Dec 6 | Dec 11 | Dec 16 | Dec 20 | Dec 24 | Dec 28 | Jan 1 | Jan 4 | Jan 11 |
| 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 | 317 | 307 | 297 | 287 | 278 | 269 | 261 | 250 | 236 |
| 32°F | 365 | 354 | 347 | 342 | 336 | 331 | 323 | 311 | 296 |
| 28°F | 365 | 365 | 365 | 365 | 365 | 363 | 358 | 351 | 343 |
| 24°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 364 |
| 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
- 88% of years
- 28°F or colder
- 44% of years
- 24°F or colder
- 9% 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
- 2,307
- Cooling degree days, base 65°F
- 1,113
- Growing degree days, base 40°F
- 7,936
- Growing degree days, base 45°F
- 6,152
- Growing degree days, base 50°F
- 4,507
- Growing degree days, base 55°F
- 3,113
- Growing degree days, base 60°F
- 1,984
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 512 | 0 | 37 |
| February | 357 | 0 | 91 |
| March | 284 | 2 | 195 |
| April | 180 | 19 | 291 |
| May | 76 | 76 | 465 |
| June | 14 | 187 | 622 |
| July | 2 | 273 | 736 |
| August | 1 | 268 | 732 |
| September | 7 | 209 | 652 |
| October | 69 | 77 | 473 |
| November | 291 | 3 | 176 |
| December | 515 | 0 | 36 |
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 11.2 km from Solano County. 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 USC00042934 (Fairfield). Public domain.