USDA Hardiness Zone 8a
Frost Dates for 73503 — Fort Sill, Oklahoma
NOAA 1991–2020 normals from Lawton, OK (1,150 ft), 6 miles south.
Updated
In Fort Sill, the last spring frost (32°F) is around March 26 in half of years and has passed by April 14 in nine years out of ten. The first fall frost comes around November 7, as early as October 21 one year in ten, leaving a typical freeze-free season of 225 days (NOAA, Lawton, OK).
- Last spring frost
- March 26
- First fall frost
- November 7
- Growing season
- 225 days
- Hardiness zone
- 8a
50% probability
50% probability
freeze-free, 50%
10 to 15°F (-12.2 to -9.4°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 40%
- Snow per year
- 1.8"
median, 1991–2020
median, 1991–2020
8 of 20 observed
NOAA normal
Frost risk by date in Fort Sill
Half of springs at Lawton, OK see their last 32°F night by March 26; only one in ten is past it by March 4, and one in ten still has one after April 14. Planting tender crops after April 3 leaves a 30% risk of a frost on them, after April 7 20%, and after April 14 10%. The 19 days between the even-odds date and the one-in-ten date is wider than at 81% of the 114 Oklahoma stations behind this site's ZIP pages.
In fall the first 32°F night comes by November 7 in half of years, as early as October 21 one year in ten, and holds off past November 22 one year in ten. A hard freeze of 28°F follows 9 days later, around November 16; in spring the one-in-ten date for 28°F is April 3, 11 days before the 32°F one. The freeze-free season lasts 225 days in a typical year, longer than at 89% of the 114 Oklahoma stations; it reaches 253 days one year in ten and falls short of 200 one year in ten. On average 70 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 12 days longer, to about April 7, and return around October 29. Severe cold of 16°F or below comes in 91% of winters, usually between December 28 and February 3.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 20 | Mar 28 | Apr 1 | Apr 4 | Apr 7 | Apr 10 | Apr 14 | Apr 19 | Apr 24 |
| 32°F | Mar 4 | Mar 12 | Mar 17 | Mar 21 | Mar 26 | Mar 31 | Apr 3 | Apr 7 | Apr 14 |
| 28°F | Feb 22 | Feb 28 | Mar 3 | Mar 7 | Mar 11 | Mar 15 | Mar 19 | Mar 26 | Apr 3 |
| 24°F | Feb 8 | Feb 17 | Feb 22 | Feb 26 | Feb 28 | Mar 3 | Mar 7 | Mar 11 | Mar 19 |
| 20°F | Jan 22 | Jan 31 | Feb 6 | Feb 11 | Feb 16 | Feb 21 | Feb 26 | Mar 1 | Mar 7 |
| 16°F91% of yrs | Dec 31 | Jan 13 | Jan 22 | Jan 29 | Feb 3 | Feb 8 | Feb 14 | Feb 21 | Feb 28 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 16 | Oct 20 | Oct 24 | Oct 27 | Oct 29 | Nov 1 | Nov 5 | Nov 8 | Nov 13 |
| 32°F | Oct 21 | Oct 27 | Nov 1 | Nov 4 | Nov 7 | Nov 10 | Nov 14 | Nov 17 | Nov 22 |
| 28°F | Oct 30 | Nov 5 | Nov 9 | Nov 13 | Nov 16 | Nov 20 | Nov 24 | Nov 30 | Dec 5 |
| 24°F | Nov 9 | Nov 16 | Nov 22 | Nov 27 | Nov 30 | Dec 3 | Dec 7 | Dec 12 | Dec 18 |
| 20°F | Nov 24 | Nov 30 | Dec 4 | Dec 9 | Dec 13 | Dec 18 | Dec 22 | Dec 28 | Jan 5 |
| 16°F91% of yrs | Dec 5 | Dec 11 | Dec 18 | Dec 22 | Dec 28 | Jan 2 | Jan 9 | Jan 19 | Feb 1 |
Freeze probabilities 1991–2020 at Lawton, OK, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 73503 →Compare Fort Sill with another place →
Weather by month in Fort Sill
July is the warmest month at Lawton, OK, averaging 96°F by day and 72°F at night; January is the coldest at 51°F and 28°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 36% of years.
Warmth for growing adds up to 5,471 growing degree days a year (base 50°F), more than at 88% of the 114 Oklahoma stations. 38% of them (2,057) have built up by the end of June, and July adds the most, 1,055. Precipitation totals 34.2 inches a year, most in May (5.0") and least in January (1.2"); May to September bring 55% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 51 | 28 | 1.2 | 100% | 23 | 14 |
| Feb | 56 | 31 | 1.7 | 100% | 13 | 38 |
| Mar | 64 | 41 | 2.4 | 92% | 6 | 171 |
| Apr | 73 | 49 | 3.3 | 36% | 1 | 332 |
| May | 82 | 59 | 5.0 | 0% | 0 | 631 |
| Jun | 90 | 68 | 4.2 | 0% | 0 | 871 |
| Jul | 96 | 72 | 2.9 | 0% | 0 | 1055 |
| Aug | 96 | 72 | 3.5 | 0% | 0 | 1046 |
| Sep | 86 | 64 | 3.1 | 0% | 0 | 740 |
| Oct | 76 | 51 | 2.9 | 29% | 1 | 422 |
| Nov | 63 | 39 | 2.1 | 97% | 8 | 130 |
| Dec | 53 | 30 | 1.9 | 100% | 19 | 21 |
Monthly normals 1991–2020 at Lawton, OK (1,150 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Medicine Pk 3W Mesonet, OK, 6 miles west of Fort Sill and 447 feet higher, has a last frost 5 days earlier (March 21), a first frost 5 days later (November 12), a season 9 days longer.
When it snows in Fort Sill, Oklahoma
Measurable snow is rare here: only 8 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Wichita Mountain Wr, OK, 14.1 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 73503
| When | What to do |
|---|---|
| January 15 – January 29 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| January 29 – February 12 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| February 26 – March 12 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| March 26 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 15 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 24 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 7 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 73503 is 6 miles from Lawton, OK, which stands at 1,150 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 73505 (Lawton). The 2023 USDA Plant Hardiness Zone Map lists ZIP 73503 in zone 8a, the band where the coldest night of the year averaged 10 to 15°F (-12.2 to -9.4°C) over 1991–2020; a zone describes winter lows, not frost dates.
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.