Coronado Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for North Island Nas. A median date has an even chance of a later freeze in spring, or an earlier one in fall.
A freeze (32°F or colder) happens in only 0 percent of years at North Island Nas, so there is no typical freeze season.
- Median at 36°F
- last January 3, first January 1
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 | Jan 23 | Jan 16 | Jan 9 | Jan 6 | Jan 3 | Jan 1 | Dec 31 | Dec 28 | Dec 18 |
| 32°F | – | – | – | – | – | – | – | – | – |
| 28°F | – | – | – | – | – | – | – | – | – |
| 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 | Dec 14 | Dec 22 | Dec 29 | Dec 31 | Jan 1 | Jan 4 | Jan 6 | Jan 13 | Jan 23 |
| 32°F | – | – | – | – | – | – | – | – | – |
| 28°F | – | – | – | – | – | – | – | – | – |
| 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 | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 |
| 32°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 |
| 28°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 |
| 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
- 11% of years
- 32°F or colder
- 0% of years
- 28°F or colder
- 0% of years
- 24°F or colder
- 0% 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
- 1,144
- Cooling degree days, base 65°F
- 760
- Growing degree days, base 40°F
- 8,741
- Growing degree days, base 45°F
- 6,916
- Growing degree days, base 50°F
- 5,094
- Growing degree days, base 55°F
- 3,322
- Growing degree days, base 60°F
- 1,815
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 232 | 4 | 238 |
| February | 189 | 4 | 236 |
| March | 165 | 9 | 309 |
| April | 113 | 15 | 353 |
| May | 54 | 29 | 440 |
| June | 16 | 55 | 489 |
| July | 1 | 148 | 612 |
| August | 0 | 205 | 670 |
| September | 1 | 177 | 626 |
| October | 17 | 90 | 538 |
| November | 112 | 23 | 362 |
| December | 245 | 2 | 223 |
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 2.2 km from Coronado. 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 USW00093112 (North Island Nas). Public domain.