Johnston, South Carolina climate: Normal weather by month, frost dates and records
Johnston's normal year runs from 33°F January nights to 93°F July afternoons, with 48.5 inches of precipitation and 1 inch of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 17.1°C, January lows of 0°C, July highs of 34°C, 1,231 mm of precipitation a year.
- NOAA stationJohnston (4 mi SW)
- Station IDUSC00384607
- Location33.78°N 81.84°W
- Elevation629 ft (192 m)
- From the center5 miles
- Population2,214
On October 23, the normal high in Johnston is 74°F and the normal low 48°F, and the chance of measurable rain or snow is 26%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Johnston.
- Jan 55° 33°
- Feb 59° 35°
- Mar 67° 41°
- Apr 76° 49°
- May 83° 57°
- Jun 90° 65°
- Jul 93° 69°
- Aug 91° 68°
- Sep 86° 62°
- Oct 76° 51°
- Nov 66° 40°
- Dec 58° 35°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Johnston each month?
July is the warmest month, with normal highs of 93°F; January the coldest, with normal lows of 33°F. The most precipitation falls in June (5.12 in), the least in October (2.98 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 55°F | 33°F | 44.0°F | 4.23 | 0.5 | 12 | <1 | 18 | 10 h 10 min |
| February | 59°F | 35°F | 47.2°F | 3.94 | 0.1 | 11 | <1 | 14 | 11 h |
| March | 67°F | 41°F | 53.9°F | 4.51 | 0.2 | 11 | <1 | 8 | 11 h 50 min |
| April | 76°F | 49°F | 62.1°F | 3.18 | 0.0 | 8 | 1 | 1 | 13 h |
| May | 83°F | 57°F | 70.3°F | 3.21 | 0.0 | 8 | 8 | <1 | 13 h 50 min |
| June | 90°F | 65°F | 77.4°F | 5.12 | 0.0 | 10 | 17 | <1 | 14 h 20 min |
| July | 93°F | 69°F | 80.9°F | 4.64 | 0.0 | 11 | 25 | <1 | 14 h 10 min |
| August | 91°F | 68°F | 79.3°F | 4.96 | 0.0 | 11 | 20 | <1 | 13 h 30 min |
| September | 86°F | 62°F | 73.9°F | 3.97 | 0.0 | 9 | 10 | <1 | 12 h 30 min |
| October | 76°F | 51°F | 63.4°F | 2.98 | 0.0 | 8 | 1 | 1 | 11 h 20 min |
| November | 66°F | 40°F | 53.1°F | 3.31 | 0.0 | 9 | <1 | 8 | 10 h 30 min |
| December | 58°F | 35°F | 46.4°F | 4.42 | 0.2 | 12 | <1 | 16 | 10 h |
| Year (annual) | 75°F | 50°F | 62.7°F | 48.47 | 1.0 | 119 | 81 | 66 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 13°C | 0°C | 6.7°C | 107 mm | 1 cm |
| February | 15°C | 2°C | 8.4°C | 100 mm | 0 cm |
| March | 19°C | 5°C | 12.2°C | 115 mm | 1 cm |
| April | 24°C | 9°C | 16.7°C | 81 mm | 0 cm |
| May | 29°C | 14°C | 21.3°C | 82 mm | 0 cm |
| June | 32°C | 18°C | 25.2°C | 130 mm | 0 cm |
| July | 34°C | 20°C | 27.2°C | 118 mm | 0 cm |
| August | 33°C | 20°C | 26.3°C | 126 mm | 0 cm |
| September | 30°C | 17°C | 23.3°C | 101 mm | 0 cm |
| October | 24°C | 11°C | 17.4°C | 76 mm | 0 cm |
| November | 19°C | 5°C | 11.7°C | 84 mm | 0 cm |
| December | 14°C | 2°C | 8.0°C | 112 mm | 1 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00384607; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Johnston?
Normal highs sit between 65°F and 85°F in March, April, May, October and November. Of those, October has the fewest days with rain (8).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00384607.
When is the last frost in Johnston?
In Johnston, the last spring frost (32°F) comes after March 26 in half of years and after April 11 in one year in ten; the first autumn frost comes before November 8 in half of years and before October 25 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- March 261 year in 10 after April 11; 9 in 10 after March 6
- First autumn frost, half of years before
- November 81 year in 10 before October 25; 9 in 10 before November 28
NOAA puts the median frost-free season at 228 days, and the season without a hard freeze (28°F) at 254 days.
A hard freeze (28°F) comes after March 13 in half of springs and before November 19 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Johnston in zone 8a in ZIP code 29832, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Johnston's NOAA station is in zone 8a: the coldest night of a typical year reaches 12°F (22 complete years).
Frost dates for every NOAA station in South Carolina · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00384607; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in Johnston?
In a normal year in Johnston, 81 days a year reach 90°F (8 of them 100°F or more), 66 nights fall to 32°F or colder and 119 days bring measurable precipitation.
- Days at 90°F or more
- 81a normal year
- Days at 100°F or more
- 8a normal year
- Nights at 32°F or colder
- 66a normal year
- Days that stay below freezing
- 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 119a normal year
- Days with 1 inch of snow or more
- fewer than 1a normal year
The highest temperature in this station's record (since 1957) is 111°F, on July 1, 2012; the lowest is −2°F, on January 22, 1985.
The wettest calendar year on that record is 1964, with 72.95 in; the snowiest season is 1972–73, with 14.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00384607; records: ACIS (NOAA Regional Climate Centers), station USC00384607. Records use complete months only; a month missing more than three days is left out.
How sunny is Johnston?
Over a year 79% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Johnston, 4.6 kWh per square metre a day. July is the sunniest month (81%) and February the cloudiest (73%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 76% | 2.9 |
| February | 73% | 3.5 |
| March | 75% | 4.5 |
| April | 80% | 5.8 |
| May | 80% | 6.2 |
| June | 81% | 6.4 |
| July | 81% | 6.2 |
| August | 80% | 5.6 |
| September | 79% | 4.9 |
| October | 79% | 4.0 |
| November | 79% | 3.1 |
| December | 74% | 2.5 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Johnston need?
A normal year in Johnston brings 2,761 heating degree days, 49% fewer than the median U.S. place (5,373), and 1,943 cooling degree days, 2.1 times the median (908). Five months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 5,366 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 650 | 1 |
| February | 500 | 2 |
| March | 356 | 12 |
| April | 146 | 59 |
| May | 30 | 196 |
| June | 1 | 375 |
| July | 0 | 491 |
| August | 0 | 445 |
| September | 9 | 276 |
| October | 122 | 74 |
| November | 367 | 10 |
| December | 579 | 2 |
| Year (annual) | 2,761 | 1,943 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00384607. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Johnston been warmer than normal lately?
2022 averaged 63.3°F, 0.6°F above the 1991-2020 normal of 62.7°F. 2 of the 2 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 63.3°F | +0.6°F | 53.00 | 0.0 |
| 2022 | 63.3°F | +0.6°F | 46.80 | 0.5 |
Over 38 complete years from 1960 to 2022, the station's annual mean temperature rose at a fitted 3.5°F per century (+0.20°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00384607; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Johnston's climate compare?
Johnston is warmer than 32 of the other 72 places with their own NOAA record in South Carolina, and wetter than 28. Across the 7,247 U.S. stations with normals, its annual mean of 62.7°F is warmer than 82%.
In the Köppen classification computed from these normals, Johnston is Cfa: temperate, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Johnston share this climate record?
2 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Trenton, SC409 people · 2 mi S
- Ward, SC124 people · 9 mi NE
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Johnston's climate
What is the coldest month in Johnston?
January, with a normal high of 55°F and a normal low of 33°F. The warmest is July (93°F by day, 69°F at night).
Does it snow in Johnston?
Yes: 1 inch in a normal year, falling on 0 days with 0.1 inch or more, the most in January (0.5 inches).
What is the rainiest month in Johnston?
June, with 5.12 in of precipitation in a normal year; the driest is October with 2.98 in.
What plant hardiness zone is Johnston in?
The USDA's 2023 map puts Johnston in zone 8a in ZIP code 29832, the nearest ZIP area. By the same method at Johnston's NOAA station, the coldest night of a typical year reaches 12°F (22 years, 1991-2020): zone 8a.
How late can frost come in Johnston?
In half of years the last 32°F night comes after March 26; in one year in ten it comes after April 11. Waiting until April 11 leaves about a one-in-ten chance of a later frost.
Nearby and next
- South Carolina climateThe statewide normals and every place in the state
- Edgefield, SC3 miles from this station, 63.7°F a year
- Graniteville, SC14 miles from this station, 61.8°F a year
- Saluda, SC16 miles from this station, 62.2°F a year
- Aiken, SC18 miles from this station, 63.9°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made