USDA Hardiness Zone 9a
Frost Dates for 29455 — Johns Island, South Carolina
NOAA 1991–2020 normals from Charleston City, SC (10 ft), 10 miles northeast.
Updated
In Johns Island, the last spring frost (32°F) is around February 4 in half of years and has passed by March 4 in nine years out of ten. The first fall frost comes around December 30, as early as December 2 one year in ten, leaving a typical freeze-free season of 321 days (NOAA, Charleston City, SC).
- Last spring frost
- February 4
- First fall frost
- December 30
- Growing season
- 321 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
- 13%
- Snow per year
- 0.3"
median, 1991–2020
median, 1991–2020
4 of 30 observed
NOAA normal
Frost risk by date in Johns Island
Half of springs at Charleston City, SC see their last 32°F night by February 4; only one in ten is past it by January 5, and one in ten still has one after March 4. Planting tender crops after February 17 leaves a 30% risk of a frost on them, after February 25 20%, and after March 4 10%. The 28 days between the even-odds date and the one-in-ten date is the widest of the 105 South Carolina stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.
In fall the first 32°F night comes by December 30 in half of years, as early as December 2 one year in ten, and holds off past January 25 one year in ten. A hard freeze of 28°F follows 9 days later, around January 8; in spring the one-in-ten date for 28°F is February 20, 12 days before the 32°F one. The freeze-free season lasts 321 days in a typical year, the longest of the 105 South Carolina stations; it reaches 357 days one year in ten and falls short of 289 one year in ten. On average 6 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 21 days longer, to about February 25, and return around December 10. A 24°F night is unusual: 25% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jan 29 | Feb 6 | Feb 13 | Feb 20 | Feb 25 | Mar 2 | Mar 6 | Mar 11 | Mar 17 |
| 32°F92% of yrs | Jan 5 | Jan 16 | Jan 24 | Jan 30 | Feb 4 | Feb 10 | Feb 17 | Feb 25 | Mar 4 |
| 28°F63% of yrs | Dec 27 | Jan 4 | Jan 10 | Jan 15 | Jan 24 | Jan 28 | Feb 1 | Feb 9 | Feb 20 |
| 24°F25% of yrs | too rare for a date | ||||||||
| 20°F4% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 20 | Nov 26 | Dec 1 | Dec 6 | Dec 10 | Dec 17 | Dec 23 | Dec 29 | Jan 7 |
| 32°F92% of yrs | Dec 2 | Dec 10 | Dec 20 | Dec 25 | Dec 30 | Jan 3 | Jan 9 | Jan 15 | Jan 25 |
| 28°F63% of yrs | Dec 15 | Dec 23 | Dec 30 | Jan 3 | Jan 8 | Jan 13 | Jan 18 | Jan 26 | Feb 3 |
| 24°F25% of yrs | too rare for a date | ||||||||
| 20°F4% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Charleston City, 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 29455 →Compare Johns Island with another place →
Weather by month in Johns Island
July is the warmest month at Charleston City, SC, averaging 88°F by day and 77°F at night; January is the coldest at 58°F and 44°F. From April to November the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 46% of years and March still brings one in 14% of years.
Warmth for growing adds up to 6,519 growing degree days a year (base 50°F), more than at 96% of the 105 South Carolina stations. 40% of them (2,630) have built up by the end of June, and July adds the most, 1,001. Precipitation totals 44.5 inches a year, most in August (6.1") and least in November (2.3"); May to September bring 54% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 58 | 44 | 2.6 | 74% | 4 | 116 |
| Feb | 60 | 46 | 2.6 | 46% | 1 | 139 |
| Mar | 66 | 52 | 3.0 | 14% | <1 | 289 |
| Apr | 72 | 60 | 3.0 | 0% | 0 | 481 |
| May | 79 | 68 | 2.6 | 0% | 0 | 729 |
| Jun | 84 | 74 | 4.9 | 0% | 0 | 878 |
| Jul | 88 | 77 | 5.1 | 0% | 0 | 1001 |
| Aug | 86 | 77 | 6.1 | 0% | 0 | 975 |
| Sep | 83 | 73 | 5.3 | 0% | 0 | 826 |
| Oct | 76 | 63 | 4.1 | 0% | 0 | 602 |
| Nov | 67 | 53 | 2.3 | 7% | <1 | 313 |
| Dec | 61 | 47 | 2.9 | 46% | 1 | 171 |
Monthly normals 1991–2020 at Charleston City, SC (10 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 International Airport, SC, 13 miles north of Johns Island, has a last frost 31 days later (March 7), a first frost 33 days earlier (November 27), a season 55 days shorter.
When it snows in Johns Island, South Carolina
Measurable snow is rare here: only 4 of 30 winters from 1991 to 2020 recorded 0.1 inch or more at Charleston International Airport, SC, 12.8 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 29455
| When | What to do |
|---|---|
| November 26 – December 10 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| December 10 – December 24 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| January 7 – January 21 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| February 4 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by October 7 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by December 16 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 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 29455 is 10 miles from Charleston City, SC, which stands at 10 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 29412 (Charleston). The 2023 USDA Plant Hardiness Zone Map lists ZIP 29455 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.