Pedley Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Riverside Muni AP. 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 January 9 and the first fall freeze around December 30, a growing season of about 362 days.
- Median at 36°F
- last February 13, first December 12
- Median at 32°F
- last January 9, first December 30
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 | Mar 13 | Mar 3 | Feb 26 | Feb 20 | Feb 13 | Feb 4 | Jan 27 | Jan 14 | Jan 2 |
| 32°F | Feb 21 | Feb 4 | Jan 29 | Jan 16 | Jan 9 | Jan 4 | Dec 30 | Dec 23 | Dec 16 |
| 28°F | – | – | – | – | – | – | – | – | – |
| 24°F | – | – | – | – | – | – | – | – | – |
| 20°F | – | – | – | – | – | – | – | – | – |
| 16°F | – | – | – | – | – | – | – | – | – |
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 | Nov 23 | Nov 30 | Dec 4 | Dec 8 | Dec 12 | Dec 16 | Dec 22 | Dec 29 | Jan 9 |
| 32°F | Dec 5 | Dec 14 | Dec 19 | Dec 24 | Dec 30 | Jan 3 | Jan 8 | Jan 21 | Feb 6 |
| 28°F | – | – | – | – | – | – | – | – | – |
| 24°F | – | – | – | – | – | – | – | – | – |
| 20°F | – | – | – | – | – | – | – | – | – |
| 16°F | – | – | – | – | – | – | – | – | – |
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 | 346 | 334 | 322 | 313 | 305 | 296 | 287 | 277 | 264 |
| 32°F | 365 | 365 | 365 | 365 | 362 | 355 | 346 | 335 | 319 |
| 28°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 |
| 24°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 |
| 20°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 |
| 16°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 |
How often it gets that cold
The share of years with at least one night at or below each temperature.
- 36°F or colder
- 98% of years
- 32°F or colder
- 58% of years
- 28°F or colder
- 7% of years
- 24°F or colder
- 0% of years
- 20°F or colder
- 0% of years
- 16°F or colder
- 0% 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
- 1,386
- Cooling degree days, base 65°F
- 1,854
- Growing degree days, base 40°F
- 9,593
- Growing degree days, base 45°F
- 7,772
- Growing degree days, base 50°F
- 5,993
- Growing degree days, base 55°F
- 4,353
- Growing degree days, base 60°F
- 2,961
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 296 | 6 | 191 |
| February | 251 | 7 | 187 |
| March | 189 | 18 | 298 |
| April | 110 | 48 | 389 |
| May | 33 | 114 | 546 |
| June | 2 | 242 | 690 |
| July | 0 | 422 | 887 |
| August | 0 | 459 | 924 |
| September | 2 | 349 | 798 |
| October | 31 | 154 | 588 |
| November | 155 | 33 | 331 |
| December | 318 | 2 | 166 |
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 4.3 km from Pedley. 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 USW00003171 (Riverside Muni AP). Public domain.