Concord Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Concord Wwtp. 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 7 and the first fall freeze around December 19, a growing season of about 346 days.
- Median at 36°F
- last February 9, first December 2
- Median at 32°F
- last January 7, first December 19
- 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 6 | Feb 28 | Feb 21 | Feb 16 | Feb 9 | Feb 3 | Jan 28 | Jan 17 | Jan 6 |
| 32°F | Feb 1 | Jan 25 | Jan 17 | Jan 11 | Jan 7 | Jan 3 | Dec 31 | Dec 26 | Dec 19 |
| 28°F | Jan 20 | Jan 10 | Jan 5 | Jan 2 | Dec 31 | Dec 29 | Dec 26 | Dec 21 | Dec 14 |
| 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 21 | Nov 26 | Dec 1 | Dec 2 | Dec 5 | Dec 10 | Dec 15 | Dec 24 |
| 32°F | Dec 1 | Dec 5 | Dec 11 | Dec 16 | Dec 19 | Dec 23 | Dec 29 | Jan 3 | Jan 12 |
| 28°F | Dec 10 | Dec 15 | Dec 20 | Dec 25 | Dec 29 | Jan 1 | Jan 2 | Jan 6 | Jan 14 |
| 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 | 333 | 319 | 310 | 303 | 297 | 290 | 282 | 273 | 264 |
| 32°F | 365 | 365 | 357 | 352 | 346 | 339 | 334 | 329 | 315 |
| 28°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 362 | 350 |
| 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
- 80% of years
- 28°F or colder
- 25% 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
- 2,029
- Cooling degree days, base 65°F
- 1,084
- Growing degree days, base 40°F
- 8,182
- Growing degree days, base 45°F
- 6,378
- Growing degree days, base 50°F
- 4,672
- Growing degree days, base 55°F
- 3,195
- Growing degree days, base 60°F
- 2,000
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 463 | 0 | 56 |
| February | 318 | 0 | 117 |
| March | 243 | 3 | 228 |
| April | 149 | 21 | 321 |
| May | 59 | 76 | 482 |
| June | 9 | 179 | 619 |
| July | 0 | 258 | 722 |
| August | 0 | 264 | 729 |
| September | 3 | 208 | 655 |
| October | 54 | 74 | 485 |
| November | 264 | 3 | 198 |
| December | 467 | 0 | 58 |
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 3.4 km from Concord. 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 USC00041967 (Concord Wwtp). Public domain.