USDA Hardiness Zone 9a
Frost Dates for 31558 — Saint Marys, Georgia
NOAA 1991–2020 normals from Brunswick 23 S, GA (25 ft), 7 miles northeast.
Updated
In Saint Marys, the last spring frost (32°F) is around February 19 in half of years and has passed by March 14 in nine years out of ten. The first fall frost comes around December 14, as early as November 21 one year in ten, leaving a typical freeze-free season of 299 days (NOAA, Brunswick 23 S, GA).
- Last spring frost
- February 19
- First fall frost
- December 14
- Growing season
- 299 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 20 observed
NOAA normal
Frost risk by date in Saint Marys
Half of springs at Brunswick 23 S, GA see their last 32°F night by February 19; only one in ten is past it by January 19, and one in ten still has one after March 14. Planting tender crops after February 28 leaves a 30% risk of a frost on them, after March 5 20%, and after March 14 10%. The 23 days between the even-odds date and the one-in-ten date is wider than at 92% 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 14 in half of years, as early as November 21 one year in ten, and holds off past January 15 one year in ten. A hard freeze of 28°F follows 20 days later, around January 3; in spring the one-in-ten date for 28°F is February 28, 14 days before the 32°F one. The freeze-free season lasts 299 days in a typical year, longer than at 98% of the 127 Georgia stations; it reaches 332 days one year in ten and falls short of 264 one year in ten. On average 12 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 14 days longer, to about March 5, and return around November 29. A 24°F night is unusual: 45% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Feb 12 | Feb 21 | Feb 26 | Mar 1 | Mar 5 | Mar 11 | Mar 16 | Mar 20 | Mar 31 |
| 32°F98% of yrs | Jan 19 | Jan 31 | Feb 7 | Feb 13 | Feb 19 | Feb 24 | Feb 28 | Mar 5 | Mar 14 |
| 28°F84% of yrs | Dec 31 | Jan 13 | Jan 23 | Jan 30 | Feb 3 | Feb 7 | Feb 12 | Feb 20 | Feb 28 |
| 24°F45% of yrs | too rare for a date | ||||||||
| 20°F8% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 11 | Nov 17 | Nov 20 | Nov 24 | Nov 29 | Dec 1 | Dec 6 | Dec 12 | Dec 22 |
| 32°F98% of yrs | Nov 21 | Nov 29 | Dec 3 | Dec 8 | Dec 14 | Dec 22 | Dec 30 | Jan 4 | Jan 15 |
| 28°F84% of yrs | Dec 2 | Dec 11 | Dec 20 | Dec 29 | Jan 3 | Jan 9 | Jan 17 | Jan 26 | Feb 7 |
| 24°F45% of yrs | too rare for a date | ||||||||
| 20°F8% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Brunswick 23 S, 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 31558 →Compare Saint Marys with another place →
Weather by month in Saint Marys
July is the warmest month at Brunswick 23 S, GA, averaging 89°F by day and 74°F at night; January is the coldest at 62°F and 43°F. From April to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 70% of years and March still brings one in 28% of years.
Warmth for growing adds up to 6,698 growing degree days a year (base 50°F), more than at 94% of the 127 Georgia stations. 41% of them (2,757) have built up by the end of June, and July adds the most, 966. Precipitation totals 47.2 inches a year, most in August (6.5") and least in November (1.7"); May to September bring 56% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 62 | 43 | 2.8 | 81% | 5 | 158 |
| Feb | 65 | 45 | 2.8 | 70% | 3 | 182 |
| Mar | 70 | 51 | 3.3 | 28% | 1 | 331 |
| Apr | 76 | 57 | 2.8 | 1% | 0 | 490 |
| May | 82 | 65 | 3.7 | 0% | 0 | 730 |
| Jun | 86 | 71 | 6.3 | 0% | 0 | 867 |
| Jul | 89 | 74 | 4.6 | 0% | 0 | 966 |
| Aug | 89 | 74 | 6.5 | 0% | 0 | 964 |
| Sep | 85 | 71 | 5.2 | 0% | 0 | 835 |
| Oct | 79 | 62 | 4.4 | 0% | 0 | 628 |
| Nov | 71 | 52 | 1.7 | 22% | 1 | 339 |
| Dec | 65 | 46 | 3.1 | 64% | 3 | 209 |
Monthly normals 1991–2020 at Brunswick 23 S, GA (25 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, Fernandina Beach, FL, 10 miles southeast of Saint Marys, has a last frost 17 days earlier (February 2), a first frost 21 days later (January 4), a season 34 days longer.
When it snows in Saint Marys, Georgia
Measurable snow is rare here: only 0 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Fernandina Beach, FL, 9.5 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 31558
| When | What to do |
|---|---|
| December 11 – December 25 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| December 25 – January 8 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| January 22 – February 5 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| February 19 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 21 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 30 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 14 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 31558 is 7 miles from Brunswick 23 S, GA, which stands at 25 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 31558 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.