USDA Hardiness Zone 9a
Frost Dates for 31522 — St Simons Island, Georgia
NOAA 1991–2020 normals from Brunswick Malcolm Mckinnon Airport, GA (16 ft), 2 miles south.
Updated
In St Simons Island, the last spring frost (32°F) is around February 9 in half of years and has passed by March 6 in nine years out of ten. The first fall frost comes around December 26, as early as November 30 one year in ten, leaving a typical freeze-free season of 312 days (NOAA, Brunswick Malcolm Mckinnon Airport, GA).
- Last spring frost
- February 9
- First fall frost
- December 26
- Growing season
- 312 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
- 0"
median, 1991–2020
median, 1991–2020
0 of 17 observed
NOAA normal
Frost risk by date in St Simons Island
Half of springs at Brunswick Malcolm Mckinnon Airport, GA see their last 32°F night by February 9; only one in ten is past it by January 11, and one in ten still has one after March 6. Planting tender crops after February 23 leaves a 30% risk of a frost on them, after February 28 20%, and after March 6 10%. The 25 days between the even-odds date and the one-in-ten date is wider than at 99% of the 127 Georgia 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 26 in half of years, as early as November 30 one year in ten, and holds off past January 19 one year in ten. A hard freeze of 28°F follows 13 days later, around January 8; in spring the one-in-ten date for 28°F is February 26, 8 days before the 32°F one. The freeze-free season lasts 312 days in a typical year, longer than at 99% of the 127 Georgia stations; it reaches 346 days one year in ten and falls short of 279 one year in ten. On average 8 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 18 days longer, to about February 27, and return around December 4. A 24°F night is unusual: 35% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Feb 1 | Feb 10 | Feb 17 | Feb 23 | Feb 27 | Mar 3 | Mar 6 | Mar 11 | Mar 18 |
| 32°F98% of yrs | Jan 11 | Jan 21 | Jan 30 | Feb 4 | Feb 9 | Feb 15 | Feb 23 | Feb 28 | Mar 6 |
| 28°F74% of yrs | Dec 30 | Jan 8 | Jan 14 | Jan 20 | Jan 27 | Jan 31 | Feb 6 | Feb 14 | Feb 26 |
| 24°F35% of yrs | too rare for a date | ||||||||
| 20°F7% of yrs | too rare for a date | ||||||||
| 16°F0% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 16 | Nov 22 | Nov 27 | Dec 1 | Dec 4 | Dec 8 | Dec 15 | Dec 22 | Jan 1 |
| 32°F98% of yrs | Nov 30 | Dec 6 | Dec 13 | Dec 20 | Dec 26 | Dec 31 | Jan 4 | Jan 9 | Jan 19 |
| 28°F74% of yrs | Dec 13 | Dec 24 | Dec 30 | Jan 3 | Jan 8 | Jan 13 | Jan 18 | Jan 27 | Feb 7 |
| 24°F35% of yrs | too rare for a date | ||||||||
| 20°F7% of yrs | too rare for a date | ||||||||
| 16°F0% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Brunswick Malcolm Mckinnon Airport, GA, 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 31522 →Compare St Simons Island with another place →
Weather by month in St Simons Island
July is the warmest month at Brunswick Malcolm Mckinnon Airport, GA, averaging 91°F by day and 76°F at night; January is the coldest at 62°F and 44°F. From April to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 56% of years and March still brings one in 19% of years.
Warmth for growing adds up to 7,170 growing degree days a year (base 50°F), more than at 99% of the 127 Georgia stations. 42% of them (2,995) have built up by the end of June, and July adds the most, 1,040. Precipitation totals 45.6 inches a year, most in September (6.0") and least in November (1.9"); May to September bring 53% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 62 | 44 | 3.2 | 81% | 4 | 161 |
| Feb | 65 | 47 | 2.8 | 56% | 2 | 200 |
| Mar | 70 | 53 | 3.3 | 19% | <1 | 370 |
| Apr | 76 | 60 | 2.8 | 0% | 0 | 540 |
| May | 83 | 68 | 2.3 | 0% | 0 | 795 |
| Jun | 88 | 74 | 5.8 | 0% | 0 | 929 |
| Jul | 91 | 76 | 4.2 | 0% | 0 | 1040 |
| Aug | 90 | 76 | 5.8 | 0% | 0 | 1015 |
| Sep | 86 | 73 | 6.0 | 0% | 0 | 874 |
| Oct | 79 | 64 | 4.7 | 0% | 0 | 660 |
| Nov | 71 | 53 | 1.9 | 12% | <1 | 367 |
| Dec | 64 | 47 | 2.8 | 56% | 2 | 218 |
Monthly normals 1991–2020 at Brunswick Malcolm Mckinnon Airport, GA (16 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, Brunswick, GA, 7 miles west of St Simons Island, has a last frost 1 day earlier (February 8), a first frost 1 day earlier (December 25), a season 2 days longer.
When it snows in St Simons Island, Georgia
Measurable snow is rare here: only 0 of 17 winters from 1991 to 2020 recorded 0.1 inch or more at Brunswick Malcolm Mckinnon Airport, GA, 1.8 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 31522
| When | What to do |
|---|---|
| December 1 – December 15 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| December 15 – December 29 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| January 12 – January 26 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| February 9 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by October 3 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by December 12 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 26 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 31522 is 2 miles from Brunswick Malcolm Mckinnon Airport, GA, which stands at 16 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 31522 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.
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.