USDA Hardiness Zone 9a
Frost Dates for 29451 — Isle Of Palms, South Carolina
NOAA 1991–2020 normals from Sullivans Is, SC (5 ft), 6 miles southwest.
Updated
In Isle Of Palms, the last spring frost (32°F) is around March 13 in half of years and has passed by March 30 in nine years out of ten. The first fall frost comes around November 30, as early as November 11 one year in ten, leaving a typical freeze-free season of 262 days (NOAA, Sullivans Is, SC).
- Last spring frost
- March 13
- First fall frost
- November 30
- Growing season
- 262 days
- Hardiness zone
- 9a
50% probability
50% probability
freeze-free, 50%
20 to 25°F (-6.7 to -3.9°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 0%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
0 of 20 observed
NOAA normal
Frost risk by date in Isle Of Palms
Half of springs at Sullivans Is, SC see their last 32°F night by March 13; only one in ten is past it by February 19, and one in ten still has one after March 30. Planting tender crops after March 21 leaves a 30% risk of a frost on them, after March 25 20%, and after March 30 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 57% of the 105 South Carolina stations behind this site's ZIP pages.
In fall the first 32°F night comes by November 30 in half of years, as early as November 11 one year in ten, and holds off past December 24 one year in ten. A hard freeze of 28°F follows 16 days later, around December 16; in spring the one-in-ten date for 28°F is March 22, 8 days before the 32°F one. The freeze-free season lasts 262 days in a typical year, longer than at 90% of the 105 South Carolina stations; it reaches 291 days one year in ten and falls short of 232 one year in ten. On average 18 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 March 25, and return around November 16. Nights of 24°F, cold enough to damage hardier plants, come in 97% of winters and 16°F in 37%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 6 | Mar 13 | Mar 17 | Mar 21 | Mar 25 | Mar 29 | Apr 1 | Apr 5 | Apr 10 |
| 32°F | Feb 19 | Feb 28 | Mar 4 | Mar 9 | Mar 13 | Mar 17 | Mar 21 | Mar 25 | Mar 30 |
| 28°F | Feb 1 | Feb 9 | Feb 17 | Feb 25 | Mar 1 | Mar 5 | Mar 10 | Mar 16 | Mar 22 |
| 24°F97% of yrs | Jan 9 | Jan 21 | Jan 29 | Feb 2 | Feb 9 | Feb 17 | Feb 27 | Mar 4 | Mar 13 |
| 20°F73% of yrs | Jan 2 | Jan 9 | Jan 15 | Jan 21 | Jan 27 | Jan 31 | Feb 7 | Feb 20 | Mar 4 |
| 16°F37% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 1 | Nov 5 | Nov 9 | Nov 12 | Nov 16 | Nov 19 | Nov 24 | Nov 29 | Dec 5 |
| 32°F | Nov 11 | Nov 17 | Nov 21 | Nov 26 | Nov 30 | Dec 2 | Dec 8 | Dec 14 | Dec 24 |
| 28°F | Nov 25 | Dec 1 | Dec 5 | Dec 11 | Dec 16 | Dec 21 | Dec 27 | Jan 2 | Jan 10 |
| 24°F97% of yrs | Dec 5 | Dec 15 | Dec 22 | Dec 28 | Jan 2 | Jan 7 | Jan 12 | Jan 18 | Jan 29 |
| 20°F73% of yrs | Dec 18 | Dec 26 | Jan 1 | Jan 5 | Jan 9 | Jan 14 | Jan 20 | Jan 27 | Feb 8 |
| 16°F37% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Sullivans Is, SC, 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 29451 →Compare Isle Of Palms with another place →
Weather by month in Isle Of Palms
July is the warmest month at Sullivans Is, SC, averaging 91°F by day and 73°F at night; January is the coldest at 59°F and 37°F. A freezing night is all but certain in every month from December to February (a 90% chance or more). From April to October the chance of a 32°F night stays under 10% each month. In spring, March still brings one in 75% of years.
Warmth for growing adds up to 6,058 growing degree days a year (base 50°F), more than at 88% of the 105 South Carolina stations. 39% of them (2,365) have built up by the end of June, and July adds the most, 994. Precipitation totals 51.6 inches a year, most in August (6.7") and least in November (3.0"); May to September bring 52% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 59 | 37 | 3.8 | 100% | 8 | 71 |
| Feb | 61 | 39 | 3.3 | 95% | 4 | 84 |
| Mar | 67 | 45 | 3.5 | 75% | 1 | 213 |
| Apr | 75 | 54 | 3.6 | 7% | <1 | 426 |
| May | 82 | 63 | 3.3 | 0% | 0 | 704 |
| Jun | 88 | 70 | 5.4 | 0% | 0 | 867 |
| Jul | 91 | 73 | 6.0 | 0% | 0 | 994 |
| Aug | 90 | 72 | 6.7 | 0% | 0 | 961 |
| Sep | 86 | 68 | 5.5 | 0% | 0 | 804 |
| Oct | 78 | 58 | 3.9 | 1% | 0 | 556 |
| Nov | 69 | 47 | 3.0 | 52% | 1 | 261 |
| Dec | 62 | 40 | 3.6 | 91% | 4 | 118 |
Monthly normals 1991–2020 at Sullivans Is, SC (5 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, Charleston City, SC, 10 miles west of Isle Of Palms, has a last frost 37 days earlier (February 4), a first frost 30 days later (December 30), a season 59 days longer.
When it snows in Isle Of Palms, South Carolina
Measurable snow is rare here: only 0 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Sullivans Is, SC, 5.9 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 29451
| When | What to do |
|---|---|
| January 2 – January 16 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| January 16 – January 30 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| February 13 – February 27 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| March 13 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 7 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 16 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 30 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 29451 is 6 miles from Sullivans Is, SC, which stands at 5 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station; its figures are presented in full for 29464 (Mount Pleasant). The 2023 USDA Plant Hardiness Zone Map lists ZIP 29451 in zone 9a, the band where the coldest night of the year averaged 20 to 25°F (-6.7 to -3.9°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across South Carolina →
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.