San Leandro Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Oakland Metro Intl 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 7 and the first fall freeze around December 23, a growing season of about 356 days.
- Median at 36°F
- last February 8, first December 4
- Median at 32°F
- last January 7, first December 23
- Median at 28°F
- last December 30, first December 28
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 7 | Feb 28 | Feb 21 | Feb 16 | Feb 8 | Feb 2 | Jan 27 | Jan 17 | Jan 3 |
| 32°F | Feb 8 | Jan 30 | Jan 22 | Jan 14 | Jan 7 | Jan 2 | Dec 29 | Dec 24 | Dec 13 |
| 28°F | Jan 15 | Jan 7 | Jan 4 | Jan 1 | Dec 30 | Dec 28 | Dec 23 | Dec 17 | Dec 9 |
| 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 15 | Nov 21 | Nov 27 | Dec 1 | Dec 4 | Dec 7 | Dec 14 | Dec 23 | Jan 5 |
| 32°F | Nov 30 | Dec 6 | Dec 10 | Dec 16 | Dec 23 | Dec 29 | Jan 3 | Jan 10 | Jan 24 |
| 28°F | Dec 6 | Dec 13 | Dec 20 | Dec 25 | Dec 28 | Dec 31 | Jan 3 | Jan 6 | Jan 12 |
| 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 | 339 | 328 | 318 | 310 | 302 | 295 | 286 | 279 | 263 |
| 32°F | 365 | 365 | 365 | 363 | 356 | 349 | 341 | 334 | 320 |
| 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
- 63% of years
- 28°F or colder
- 11% 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
- 2,690
- Cooling degree days, base 65°F
- 175
- Growing degree days, base 40°F
- 6,610
- Growing degree days, base 45°F
- 4,801
- Growing degree days, base 50°F
- 3,106
- Growing degree days, base 55°F
- 1,685
- Growing degree days, base 60°F
- 681
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 470 | 0 | 48 |
| February | 351 | 0 | 90 |
| March | 309 | 1 | 164 |
| April | 234 | 4 | 221 |
| May | 170 | 12 | 307 |
| June | 92 | 24 | 383 |
| July | 59 | 25 | 431 |
| August | 50 | 39 | 454 |
| September | 56 | 50 | 444 |
| October | 133 | 20 | 352 |
| November | 305 | 1 | 157 |
| December | 462 | 0 | 56 |
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 5.7 km from San Leandro. 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 USW00023230 (Oakland Metro Intl AP). Public domain.