New London Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Saverton L&d 22. 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 April 4 and the first fall freeze around November 4, a growing season of about 212 days.
- Median at 36°F
- last April 14, first October 24
- Median at 32°F
- last April 4, first November 4
- Median at 28°F
- last March 26, first November 14
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 30 | Apr 25 | Apr 21 | Apr 18 | Apr 14 | Apr 11 | Apr 8 | Apr 5 | Apr 2 |
| 32°F | Apr 19 | Apr 13 | Apr 9 | Apr 7 | Apr 4 | Apr 2 | Mar 31 | Mar 25 | Mar 20 |
| 28°F | Apr 8 | Apr 4 | Apr 1 | Mar 30 | Mar 26 | Mar 22 | Mar 18 | Mar 14 | Mar 8 |
| 24°F | Apr 2 | Mar 28 | Mar 23 | Mar 19 | Mar 15 | Mar 12 | Mar 8 | Mar 4 | Feb 28 |
| 20°F | Mar 24 | Mar 17 | Mar 13 | Mar 10 | Mar 6 | Mar 3 | Mar 1 | Feb 26 | Feb 19 |
| 16°F | Mar 16 | Mar 10 | Mar 7 | Mar 4 | Mar 1 | Feb 27 | Feb 21 | Feb 16 | Feb 6 |
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 | Oct 12 | Oct 17 | Oct 20 | Oct 22 | Oct 24 | Oct 26 | Oct 29 | Nov 1 | Nov 5 |
| 32°F | Oct 23 | Oct 28 | Oct 31 | Nov 1 | Nov 4 | Nov 6 | Nov 9 | Nov 13 | Nov 18 |
| 28°F | Nov 1 | Nov 4 | Nov 8 | Nov 10 | Nov 14 | Nov 16 | Nov 20 | Nov 24 | Nov 30 |
| 24°F | Nov 7 | Nov 11 | Nov 15 | Nov 19 | Nov 22 | Nov 26 | Nov 30 | Dec 3 | Dec 9 |
| 20°F | Nov 14 | Nov 20 | Nov 25 | Nov 29 | Dec 1 | Dec 5 | Dec 9 | Dec 13 | Dec 19 |
| 16°F | Nov 23 | Nov 30 | Dec 3 | Dec 6 | Dec 11 | Dec 16 | Dec 20 | Dec 24 | Dec 30 |
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 | 210 | 204 | 199 | 195 | 191 | 187 | 183 | 179 | 173 |
| 32°F | 234 | 225 | 220 | 216 | 212 | 209 | 205 | 201 | 194 |
| 28°F | 257 | 248 | 243 | 238 | 233 | 229 | 224 | 219 | 211 |
| 24°F | 276 | 268 | 261 | 257 | 252 | 248 | 243 | 237 | 229 |
| 20°F | 293 | 284 | 279 | 274 | 268 | 263 | 259 | 253 | 246 |
| 16°F | 310 | 302 | 295 | 290 | 285 | 280 | 275 | 268 | 261 |
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
- 100% of years
- 28°F or colder
- 100% of years
- 24°F or colder
- 100% of years
- 20°F or colder
- 100% of years
- 16°F or colder
- 100% 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
- 5,027
- Cooling degree days, base 65°F
- 1,434
- Growing degree days, base 40°F
- 6,561
- Growing degree days, base 45°F
- 5,276
- Growing degree days, base 50°F
- 4,121
- Growing degree days, base 55°F
- 3,099
- Growing degree days, base 60°F
- 2,199
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 1,123 | 0 | 3 |
| February | 895 | 0 | 8 |
| March | 685 | 3 | 55 |
| April | 331 | 18 | 196 |
| May | 101 | 107 | 473 |
| June | 9 | 296 | 738 |
| July | 0 | 422 | 887 |
| August | 1 | 377 | 841 |
| September | 45 | 174 | 580 |
| October | 264 | 33 | 268 |
| November | 604 | 2 | 66 |
| December | 969 | 0 | 7 |
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 14.1 km from New London. 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 USC00237578 (Saverton L&d 22). Public domain.