Homer Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Ogden. 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 20 and the first fall freeze around October 21, a growing season of about 182 days.
- Median at 36°F
- last May 2, first October 12
- Median at 32°F
- last April 20, first October 21
- Median at 28°F
- last April 9, first October 31
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 | May 16 | May 12 | May 8 | May 5 | May 2 | Apr 28 | Apr 25 | Apr 22 | Apr 18 |
| 32°F | May 7 | May 1 | Apr 26 | Apr 23 | Apr 20 | Apr 18 | Apr 15 | Apr 12 | Apr 7 |
| 28°F | Apr 25 | Apr 19 | Apr 15 | Apr 12 | Apr 9 | Apr 7 | Apr 5 | Apr 2 | Mar 29 |
| 24°F | Apr 14 | Apr 7 | Apr 4 | Apr 2 | Mar 31 | Mar 28 | Mar 24 | Mar 21 | Mar 14 |
| 20°F | Apr 3 | Mar 30 | Mar 27 | Mar 23 | Mar 20 | Mar 17 | Mar 13 | Mar 9 | Mar 4 |
| 16°F | Mar 27 | Mar 21 | Mar 17 | Mar 15 | Mar 11 | Mar 8 | Mar 5 | Mar 1 | Feb 23 |
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 27 | Oct 1 | Oct 6 | Oct 9 | Oct 12 | Oct 15 | Oct 17 | Oct 20 | Oct 23 |
| 32°F | Oct 8 | Oct 13 | Oct 16 | Oct 19 | Oct 21 | Oct 24 | Oct 26 | Oct 29 | Nov 2 |
| 28°F | Oct 19 | Oct 23 | Oct 26 | Oct 29 | Oct 31 | Nov 1 | Nov 5 | Nov 9 | Nov 14 |
| 24°F | Oct 30 | Nov 1 | Nov 5 | Nov 7 | Nov 11 | Nov 13 | Nov 17 | Nov 21 | Nov 26 |
| 20°F | Nov 5 | Nov 10 | Nov 13 | Nov 17 | Nov 20 | Nov 23 | Nov 27 | Dec 1 | Dec 7 |
| 16°F | Nov 11 | Nov 17 | Nov 22 | Nov 26 | Nov 29 | Dec 3 | Dec 7 | Dec 13 | Dec 19 |
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 | 180 | 174 | 169 | 165 | 161 | 157 | 153 | 148 | 141 |
| 32°F | 200 | 194 | 189 | 186 | 182 | 178 | 174 | 169 | 160 |
| 28°F | 222 | 215 | 211 | 207 | 203 | 199 | 195 | 190 | 183 |
| 24°F | 246 | 238 | 233 | 229 | 225 | 221 | 216 | 211 | 206 |
| 20°F | 267 | 259 | 254 | 249 | 245 | 241 | 236 | 230 | 223 |
| 16°F | 290 | 281 | 274 | 269 | 264 | 259 | 253 | 248 | 239 |
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
- 5,638
- Cooling degree days, base 65°F
- 992
- Growing degree days, base 40°F
- 5,754
- Growing degree days, base 45°F
- 4,548
- Growing degree days, base 50°F
- 3,471
- Growing degree days, base 55°F
- 2,518
- Growing degree days, base 60°F
- 1,692
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 1,206 | 0 | 1 |
| February | 973 | 0 | 3 |
| March | 765 | 3 | 45 |
| April | 390 | 8 | 151 |
| May | 150 | 83 | 408 |
| June | 10 | 214 | 654 |
| July | 3 | 292 | 755 |
| August | 4 | 244 | 705 |
| September | 72 | 126 | 505 |
| October | 332 | 22 | 209 |
| November | 699 | 1 | 33 |
| December | 1,035 | 0 | 3 |
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 8.3 km from Homer. 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 USC00116344 (Ogden). Public domain.