Norco Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Chino AP. 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 17 and the first fall freeze around December 19, a growing season of about 335 days.
- Median at 36°F
- last February 24, first December 1
- Median at 32°F
- last January 17, first December 19
- Median at 28°F
- last January 3, first December 30
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 29 | Mar 15 | Mar 6 | Feb 28 | Feb 24 | Feb 18 | Feb 12 | Feb 3 | Jan 21 |
| 32°F | Feb 22 | Feb 11 | Feb 3 | Jan 28 | Jan 17 | Jan 11 | Jan 5 | Dec 30 | Dec 18 |
| 28°F | Jan 28 | Jan 18 | Jan 12 | Jan 7 | Jan 3 | Dec 31 | Dec 25 | Dec 20 | 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 | Nov 12 | Nov 19 | Nov 24 | Nov 28 | Dec 1 | Dec 4 | Dec 8 | Dec 12 | Dec 18 |
| 32°F | Nov 27 | Dec 5 | Dec 10 | Dec 14 | Dec 19 | Dec 23 | Dec 28 | Jan 2 | Jan 17 |
| 28°F | Dec 7 | Dec 15 | Dec 21 | Dec 25 | Dec 30 | Jan 2 | Jan 6 | Jan 12 | Jan 23 |
| 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 | 316 | 302 | 293 | 285 | 278 | 270 | 263 | 255 | 241 |
| 32°F | 365 | 358 | 349 | 342 | 335 | 328 | 319 | 308 | 293 |
| 28°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 357 | 346 |
| 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
- 85% of years
- 28°F or colder
- 29% of years
- 24°F or colder
- 2% 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
- 1,387
- Cooling degree days, base 65°F
- 1,817
- Growing degree days, base 40°F
- 9,555
- Growing degree days, base 45°F
- 7,733
- Growing degree days, base 50°F
- 5,949
- Growing degree days, base 55°F
- 4,302
- Growing degree days, base 60°F
- 2,908
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 295 | 4 | 186 |
| February | 247 | 5 | 186 |
| March | 195 | 14 | 287 |
| April | 107 | 43 | 386 |
| May | 30 | 114 | 549 |
| June | 2 | 244 | 692 |
| July | 0 | 412 | 877 |
| August | 0 | 457 | 922 |
| September | 1 | 348 | 796 |
| October | 28 | 149 | 586 |
| November | 157 | 28 | 323 |
| December | 325 | 1 | 158 |
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 9.4 km from Norco. 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 USW00003179 (Chino AP). Public domain.