Lucerne Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Thermopolis 9NE. 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 24 and the first fall freeze around September 16, a growing season of about 112 days.
- Median at 36°F
- last June 9, first September 7
- Median at 32°F
- last May 24, first September 16
- Median at 28°F
- last May 11, first September 24
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 28 | Jun 21 | Jun 17 | Jun 13 | Jun 9 | Jun 6 | Jun 3 | Jun 1 | May 26 |
| 32°F | Jun 9 | Jun 3 | May 31 | May 28 | May 24 | May 22 | May 19 | May 16 | May 12 |
| 28°F | May 24 | May 19 | May 16 | May 14 | May 11 | May 8 | May 6 | May 4 | Apr 30 |
| 24°F | May 11 | May 7 | May 4 | May 2 | Apr 30 | Apr 28 | Apr 24 | Apr 20 | Apr 15 |
| 20°F | May 2 | Apr 29 | Apr 25 | Apr 22 | Apr 18 | Apr 15 | Apr 11 | Apr 6 | Apr 1 |
| 16°F | Apr 24 | Apr 18 | Apr 14 | Apr 10 | Apr 6 | Apr 2 | Mar 31 | Mar 25 | Mar 17 |
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 | Aug 27 | Aug 31 | Sep 2 | Sep 5 | Sep 7 | Sep 9 | Sep 12 | Sep 14 | Sep 18 |
| 32°F | Sep 4 | Sep 8 | Sep 11 | Sep 13 | Sep 16 | Sep 19 | Sep 21 | Sep 24 | Sep 29 |
| 28°F | Sep 13 | Sep 16 | Sep 20 | Sep 22 | Sep 24 | Sep 27 | Sep 30 | Oct 4 | Oct 8 |
| 24°F | Sep 20 | Sep 25 | Sep 28 | Oct 1 | Oct 4 | Oct 7 | Oct 12 | Oct 15 | Oct 20 |
| 20°F | Sep 29 | Oct 3 | Oct 7 | Oct 12 | Oct 15 | Oct 18 | Oct 21 | Oct 24 | Oct 28 |
| 16°F | Oct 7 | Oct 14 | Oct 18 | Oct 21 | Oct 25 | Oct 27 | Oct 30 | Nov 2 | Nov 8 |
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 | 107 | 101 | 96 | 92 | 89 | 84 | 80 | 74 | 67 |
| 32°F | 130 | 124 | 119 | 116 | 112 | 108 | 104 | 99 | 94 |
| 28°F | 153 | 147 | 143 | 139 | 135 | 131 | 128 | 123 | 116 |
| 24°F | 177 | 170 | 165 | 160 | 157 | 153 | 150 | 145 | 139 |
| 20°F | 203 | 194 | 188 | 183 | 178 | 173 | 168 | 164 | 156 |
| 16°F | 225 | 215 | 209 | 205 | 200 | 195 | 190 | 184 | 176 |
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
- 8,450
- Cooling degree days, base 65°F
- 310
- Growing degree days, base 40°F
- 3,655
- Growing degree days, base 45°F
- 2,696
- Growing degree days, base 50°F
- 1,890
- Growing degree days, base 55°F
- 1,225
- Growing degree days, base 60°F
- 693
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 1,536 | 0 | 0 |
| February | 1,180 | 0 | 0 |
| March | 954 | 0 | 2 |
| April | 669 | 0 | 20 |
| May | 404 | 2 | 133 |
| June | 141 | 37 | 352 |
| July | 19 | 151 | 596 |
| August | 43 | 108 | 530 |
| September | 271 | 11 | 224 |
| October | 679 | 0 | 32 |
| November | 1,047 | 0 | 1 |
| December | 1,508 | 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 3.3 km from Lucerne. 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 USC00488884 (Thermopolis 9NE). Public domain.