Vesper Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Wisconsin Rapids. 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 9 and the first fall freeze around September 30, a growing season of about 142 days.
- Median at 36°F
- last May 21, first September 21
- Median at 32°F
- last May 9, first September 30
- Median at 28°F
- last April 30, first October 10
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 3 | May 30 | May 27 | May 24 | May 21 | May 18 | May 15 | May 11 | May 7 |
| 32°F | May 24 | May 19 | May 15 | May 11 | May 9 | May 6 | May 3 | Apr 30 | Apr 26 |
| 28°F | May 14 | May 8 | May 4 | May 2 | Apr 30 | Apr 27 | Apr 24 | Apr 20 | Apr 15 |
| 24°F | May 3 | Apr 28 | Apr 24 | Apr 21 | Apr 18 | Apr 15 | Apr 12 | Apr 8 | Apr 4 |
| 20°F | Apr 23 | Apr 18 | Apr 14 | Apr 10 | Apr 7 | Apr 4 | Apr 2 | Mar 31 | Mar 24 |
| 16°F | Apr 14 | Apr 9 | Apr 5 | Apr 3 | Apr 1 | Mar 29 | Mar 25 | Mar 21 | Mar 16 |
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 8 | Sep 13 | Sep 16 | Sep 19 | Sep 21 | Sep 24 | Sep 26 | Sep 30 | Oct 4 |
| 32°F | Sep 17 | Sep 21 | Sep 24 | Sep 27 | Sep 30 | Oct 2 | Oct 5 | Oct 8 | Oct 13 |
| 28°F | Sep 25 | Sep 30 | Oct 3 | Oct 7 | Oct 10 | Oct 13 | Oct 16 | Oct 19 | Oct 24 |
| 24°F | Oct 5 | Oct 12 | Oct 16 | Oct 19 | Oct 22 | Oct 25 | Oct 27 | Oct 30 | Nov 3 |
| 20°F | Oct 18 | Oct 24 | Oct 28 | Oct 31 | Nov 1 | Nov 4 | Nov 7 | Nov 11 | Nov 17 |
| 16°F | Oct 31 | Nov 2 | Nov 6 | Nov 8 | Nov 11 | Nov 14 | Nov 17 | Nov 21 | Nov 25 |
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 | 142 | 135 | 131 | 127 | 124 | 120 | 116 | 111 | 105 |
| 32°F | 161 | 155 | 150 | 146 | 142 | 139 | 135 | 130 | 123 |
| 28°F | 181 | 175 | 171 | 166 | 162 | 158 | 153 | 148 | 141 |
| 24°F | 204 | 198 | 193 | 189 | 185 | 181 | 176 | 171 | 162 |
| 20°F | 226 | 219 | 214 | 210 | 207 | 203 | 199 | 194 | 187 |
| 16°F | 244 | 238 | 232 | 229 | 225 | 221 | 217 | 212 | 207 |
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
- 8,158
- Cooling degree days, base 65°F
- 460
- Growing degree days, base 40°F
- 4,129
- Growing degree days, base 45°F
- 3,149
- Growing degree days, base 50°F
- 2,285
- Growing degree days, base 55°F
- 1,540
- Growing degree days, base 60°F
- 926
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 1,556 | 0 | 0 |
| February | 1,303 | 0 | 0 |
| March | 1,081 | 0 | 11 |
| April | 649 | 1 | 45 |
| May | 308 | 22 | 219 |
| June | 79 | 98 | 470 |
| July | 21 | 173 | 617 |
| August | 41 | 126 | 550 |
| September | 208 | 36 | 294 |
| October | 574 | 3 | 74 |
| November | 970 | 0 | 5 |
| December | 1,369 | 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 16.3 km from Vesper. 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 USC00479335 (Wisconsin Rapids). Public domain.