Reseda Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Woodland Hills Pierce College. 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 24 and the first fall freeze around December 15, a growing season of about 329 days.
- Median at 36°F
- last March 2, first November 29
- Median at 32°F
- last January 24, first December 15
- Median at 28°F
- last December 31, first December 26
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 | Apr 7 | Mar 28 | Mar 15 | Mar 8 | Mar 2 | Feb 27 | Feb 21 | Feb 14 | Jan 30 |
| 32°F | Mar 5 | Feb 23 | Feb 12 | Feb 3 | Jan 24 | Jan 15 | Jan 6 | Dec 31 | Dec 21 |
| 28°F | Feb 1 | Jan 19 | Jan 11 | Jan 4 | Dec 31 | Dec 27 | Dec 22 | Dec 13 | Dec 5 |
| 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 12 | Nov 18 | Nov 23 | Nov 26 | Nov 29 | Dec 2 | Dec 6 | Dec 11 | Dec 19 |
| 32°F | Nov 27 | Dec 2 | Dec 6 | Dec 11 | Dec 15 | Dec 22 | Dec 28 | Jan 4 | Jan 26 |
| 28°F | Dec 1 | Dec 9 | Dec 15 | Dec 22 | Dec 26 | Dec 31 | Jan 4 | Jan 11 | Jan 25 |
| 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 | 309 | 293 | 283 | 276 | 271 | 263 | 253 | 245 | 234 |
| 32°F | 365 | 353 | 344 | 336 | 329 | 320 | 308 | 296 | 277 |
| 28°F | 365 | 365 | 365 | 365 | 365 | 365 | 362 | 352 | 341 |
| 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
- 100% of years
- 32°F or colder
- 91% of years
- 28°F or colder
- 35% of years
- 24°F or colder
- 5% 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
- 1,336
- Cooling degree days, base 65°F
- 1,819
- Growing degree days, base 40°F
- 9,608
- Growing degree days, base 45°F
- 7,786
- Growing degree days, base 50°F
- 6,002
- Growing degree days, base 55°F
- 4,351
- Growing degree days, base 60°F
- 2,938
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 272 | 7 | 211 |
| February | 238 | 9 | 201 |
| March | 178 | 22 | 312 |
| April | 111 | 53 | 393 |
| May | 48 | 119 | 536 |
| June | 7 | 238 | 681 |
| July | 0 | 401 | 866 |
| August | 0 | 437 | 902 |
| September | 2 | 338 | 786 |
| October | 31 | 156 | 591 |
| November | 148 | 34 | 339 |
| December | 300 | 5 | 184 |
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 4.1 km from Reseda. 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 USC00049785 (Woodland Hills Pierce College). Public domain.