Alfred Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Sanford 2 Nnw. 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 May 16 and the first fall freeze around September 30, a growing season of about 136 days.
- Median at 36°F
- last May 26, first September 20
- Median at 32°F
- last May 16, first September 30
- Median at 28°F
- last May 2, first October 7
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 | Jun 6 | Jun 3 | Jun 1 | May 29 | May 26 | May 24 | May 22 | May 19 | May 15 |
| 32°F | May 29 | May 24 | May 21 | May 18 | May 16 | May 13 | May 10 | May 7 | May 2 |
| 28°F | May 17 | May 12 | May 8 | May 5 | May 2 | Apr 30 | Apr 28 | Apr 25 | Apr 21 |
| 24°F | May 2 | Apr 29 | Apr 25 | Apr 23 | Apr 20 | Apr 17 | Apr 14 | Apr 10 | Apr 6 |
| 20°F | Apr 20 | Apr 16 | Apr 12 | Apr 8 | Apr 6 | Apr 4 | Apr 2 | Mar 31 | Mar 27 |
| 16°F | Apr 8 | Apr 4 | Apr 2 | Mar 31 | Mar 29 | Mar 26 | Mar 22 | Mar 18 | Mar 14 |
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 | Sep 6 | Sep 12 | Sep 15 | Sep 18 | Sep 20 | Sep 22 | Sep 25 | Sep 28 | Oct 1 |
| 32°F | Sep 18 | Sep 22 | Sep 25 | Sep 28 | Sep 30 | Oct 1 | Oct 4 | Oct 6 | Oct 10 |
| 28°F | Sep 28 | Oct 1 | Oct 3 | Oct 5 | Oct 7 | Oct 10 | Oct 13 | Oct 17 | Oct 24 |
| 24°F | Oct 5 | Oct 10 | Oct 13 | Oct 16 | Oct 20 | Oct 24 | Oct 28 | Nov 1 | Nov 5 |
| 20°F | Oct 18 | Oct 24 | Oct 27 | Oct 31 | Nov 2 | Nov 5 | Nov 9 | Nov 13 | Nov 19 |
| 16°F | Oct 30 | Nov 5 | Nov 10 | Nov 13 | Nov 16 | Nov 19 | Nov 23 | Nov 27 | Dec 1 |
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 | 130 | 125 | 121 | 118 | 114 | 111 | 108 | 103 | 97 |
| 32°F | 153 | 147 | 143 | 139 | 136 | 133 | 129 | 124 | 118 |
| 28°F | 177 | 170 | 164 | 161 | 157 | 153 | 150 | 146 | 139 |
| 24°F | 204 | 197 | 192 | 188 | 183 | 179 | 175 | 170 | 162 |
| 20°F | 230 | 224 | 217 | 213 | 209 | 205 | 200 | 195 | 187 |
| 16°F | 251 | 246 | 241 | 236 | 233 | 229 | 224 | 219 | 211 |
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
- 7,431
- Cooling degree days, base 65°F
- 351
- Growing degree days, base 40°F
- 4,015
- Growing degree days, base 45°F
- 2,997
- Growing degree days, base 50°F
- 2,120
- Growing degree days, base 55°F
- 1,381
- Growing degree days, base 60°F
- 783
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 1,370 | 0 | 0 |
| February | 1,168 | 0 | 0 |
| March | 1,032 | 0 | 4 |
| April | 643 | 1 | 40 |
| May | 343 | 11 | 170 |
| June | 110 | 60 | 402 |
| July | 22 | 137 | 580 |
| August | 33 | 108 | 539 |
| September | 186 | 33 | 307 |
| October | 527 | 1 | 69 |
| November | 827 | 0 | 9 |
| December | 1,170 | 0 | 0 |
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 5.5 km from Alfred. 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 USC00177479 (Sanford 2 Nnw). Public domain.