Houston Frost Dates and Growing Season
Frost and the growing season
NOAA's 1991-2020 freeze probabilities for Houston-Port. 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 February 2 and the first fall freeze around December 25, a growing season of about 327 days.
- Median at 36°F
- last February 24, first December 2
- Median at 32°F
- last February 2, first December 25
- Median at 28°F
- last January 23, first January 5
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 16 | Mar 9 | Mar 4 | Feb 28 | Feb 24 | Feb 17 | Feb 8 | Jan 31 | Jan 22 |
| 32°F | Mar 5 | Feb 28 | Feb 18 | Feb 9 | Feb 2 | Jan 28 | Jan 21 | Jan 13 | Dec 31 |
| 28°F | Feb 25 | Feb 11 | Feb 2 | Jan 27 | Jan 23 | Jan 17 | Jan 11 | Jan 2 | Dec 24 |
| 24°F | Feb 16 | Feb 3 | Jan 28 | Jan 22 | Jan 15 | Jan 11 | Jan 7 | Jan 3 | Dec 29 |
| 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 19 | Nov 25 | Nov 30 | Dec 2 | Dec 7 | Dec 13 | Dec 22 | Jan 1 |
| 32°F | Nov 27 | Dec 2 | Dec 8 | Dec 17 | Dec 25 | Dec 31 | Jan 4 | Jan 10 | Jan 21 |
| 28°F | Dec 8 | Dec 19 | Dec 28 | Jan 1 | Jan 5 | Jan 10 | Jan 16 | Jan 26 | Feb 9 |
| 24°F | Dec 25 | Jan 1 | Jan 3 | Jan 7 | Jan 10 | Jan 15 | Jan 22 | Feb 1 | Feb 14 |
| 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 | 326 | 313 | 304 | 295 | 287 | 279 | 272 | 265 | 256 |
| 32°F | 365 | 352 | 343 | 336 | 327 | 319 | 308 | 299 | 285 |
| 28°F | 365 | 365 | 365 | 365 | 364 | 354 | 345 | 336 | 323 |
| 24°F | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 365 | 356 |
| 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
- 90% of years
- 28°F or colder
- 55% of years
- 24°F or colder
- 18% of years
- 20°F or colder
- 4% 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
- 1,222
- Cooling degree days, base 65°F
- 3,280
- Growing degree days, base 40°F
- 11,197
- Growing degree days, base 45°F
- 9,411
- Growing degree days, base 50°F
- 7,687
- Growing degree days, base 55°F
- 6,069
- Growing degree days, base 60°F
- 4,591
Growing degree days by month, base 50°F
Heating and cooling by month
| Month | Heating DD | Cooling DD | Growing DD 50 |
|---|---|---|---|
| January | 365 | 11 | 177 |
| February | 226 | 24 | 244 |
| March | 116 | 69 | 425 |
| April | 27 | 179 | 602 |
| May | 1 | 379 | 843 |
| June | 0 | 541 | 991 |
| July | 0 | 620 | 1,085 |
| August | 0 | 637 | 1,102 |
| September | 0 | 474 | 924 |
| October | 24 | 250 | 692 |
| November | 149 | 72 | 385 |
| December | 314 | 23 | 217 |
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 8.2 km from Houston. 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 USC00414326 (Houston-Port). Public domain.