Union, South Carolina climate: Normal weather by month, frost dates and records
Union's normal year runs from 29°F January nights to 90°F July afternoons, with 45.3 inches of precipitation and 2 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 15.8°C, January lows of −2°C, July highs of 32°C, 1,149 mm of precipitation a year.
- NOAA stationUnion (8 mi S)
- Station IDUSC00388786
- Location34.61°N 81.66°W
- Elevation480 ft (146 m)
- Population7,988
On October 23, the normal high in Union is 71°F and the normal low 44°F, and the chance of measurable rain or snow is 23%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Union.
- Jan 53° 29°
- Feb 57° 32°
- Mar 65° 38°
- Apr 74° 47°
- May 81° 55°
- Jun 87° 65°
- Jul 90° 68°
- Aug 89° 67°
- Sep 83° 61°
- Oct 74° 48°
- Nov 63° 37°
- Dec 55° 32°
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 Union each month?
July is the warmest month, with normal highs of 90°F; January the coldest, with normal lows of 29°F. The most precipitation falls in March (4.29 in), the least in May (3.13 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 53°F | 29°F | 41.0°F | 4.19 | 0.9 | 9 | <1 | 21 | 10 h |
| February | 57°F | 32°F | 44.7°F | 3.61 | 0.6 | 9 | <1 | 17 | 11 h |
| March | 65°F | 38°F | 51.1°F | 4.29 | 0.4 | 10 | <1 | 12 | 11 h 50 min |
| April | 74°F | 47°F | 60.3°F | 3.75 | 0.0 | 8 | 1 | 3 | 13 h |
| May | 81°F | 55°F | 68.0°F | 3.13 | 0.0 | 8 | 3 | <1 | 14 h |
| June | 87°F | 65°F | 75.8°F | 4.09 | 0.0 | 10 | 11 | <1 | 14 h 30 min |
| July | 90°F | 68°F | 79.3°F | 3.67 | 0.0 | 9 | 19 | <1 | 14 h 20 min |
| August | 89°F | 67°F | 78.0°F | 3.99 | 0.0 | 9 | 15 | <1 | 13 h 30 min |
| September | 83°F | 61°F | 72.1°F | 3.37 | 0.0 | 7 | 7 | <1 | 12 h 30 min |
| October | 74°F | 48°F | 60.7°F | 3.33 | 0.0 | 7 | <1 | 2 | 11 h 20 min |
| November | 63°F | 37°F | 50.2°F | 3.56 | 0.0 | 8 | <1 | 13 | 10 h 20 min |
| December | 55°F | 32°F | 43.5°F | 4.27 | 0.0 | 10 | <1 | 20 | 9 h 50 min |
| Year (annual) | 73°F | 48°F | 60.4°F | 45.25 | 1.9 | 104 | 56 | 87 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 12°C | −2°C | 5.0°C | 106 mm | 2 cm |
| February | 14°C | 0°C | 7.1°C | 92 mm | 2 cm |
| March | 18°C | 3°C | 10.6°C | 109 mm | 1 cm |
| April | 23°C | 8°C | 15.7°C | 95 mm | 0 cm |
| May | 27°C | 13°C | 20.0°C | 80 mm | 0 cm |
| June | 31°C | 18°C | 24.3°C | 104 mm | 0 cm |
| July | 32°C | 20°C | 26.3°C | 93 mm | 0 cm |
| August | 32°C | 20°C | 25.6°C | 101 mm | 0 cm |
| September | 28°C | 16°C | 22.3°C | 86 mm | 0 cm |
| October | 23°C | 9°C | 15.9°C | 85 mm | 0 cm |
| November | 17°C | 3°C | 10.1°C | 90 mm | 0 cm |
| December | 13°C | 0°C | 6.4°C | 108 mm | 0 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00388786; 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 Union?
Normal highs sit between 65°F and 85°F in April, May, September and October. Of those, October has the fewest days with rain (7).
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 USC00388786.
When is the last frost in Union?
In Union, the last spring frost (32°F) comes after April 6 in half of years and after April 21 in one year in ten; the first autumn frost comes before October 30 in half of years and before October 17 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
- April 61 year in 10 after April 21; 9 in 10 after March 21
- First autumn frost, half of years before
- October 301 year in 10 before October 17; 9 in 10 before November 12
NOAA puts the median frost-free season at 207 days, and the season without a hard freeze (28°F) at 230 days.
A hard freeze (28°F) comes after March 26 in half of springs and before November 9 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Union in zone 8a in ZIP code 29379, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Union's NOAA station is in zone 8a: the coldest night of a typical year reaches 10°F (21 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 USC00388786; 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 Union?
In a normal year in Union, 56 days a year reach 90°F (3 of them 100°F or more), 87 nights fall to 32°F or colder and 104 days bring measurable precipitation.
- Days at 90°F or more
- 56a normal year
- Days at 100°F or more
- 3a normal year
- Nights at 32°F or colder
- 87a normal year
- Days that stay below freezing
- 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 104a normal year
- Days with 1 inch of snow or more
- 1a normal year
The highest temperature in this station's record (since 1949) is 108°F, on July 29, 1952; the lowest is −1°F, on January 21, 1985.
The wettest calendar year on that record is 1971, with 65.74 in; the snowiest season is 1959–60, with 14.1 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00388786; records: ACIS (NOAA Regional Climate Centers), station USC00388786. Records use complete months only; a month missing more than three days is left out.
How sunny is Union?
Over a year 78% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Union, 4.5 kWh per square metre a day. June is the sunniest month (82%) and February the cloudiest (71%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 75% | 2.7 |
| February | 71% | 3.4 |
| March | 74% | 4.4 |
| April | 78% | 5.6 |
| May | 79% | 6.1 |
| June | 82% | 6.4 |
| July | 81% | 6.1 |
| August | 80% | 5.5 |
| September | 79% | 4.8 |
| October | 79% | 3.9 |
| November | 79% | 3.0 |
| December | 73% | 2.4 |
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 Union need?
A normal year in Union brings 3,296 heating degree days, 39% fewer than the median U.S. place (5,373), and 1,649 cooling degree days, 82% more than 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 4,790 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 746 | 0 |
| February | 569 | 1 |
| March | 437 | 7 |
| April | 184 | 42 |
| May | 49 | 142 |
| June | 3 | 328 |
| July | 0 | 445 |
| August | 0 | 403 |
| September | 17 | 231 |
| October | 177 | 45 |
| November | 449 | 5 |
| December | 666 | 1 |
| Year (annual) | 3,296 | 1,649 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00388786. 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 Union been warmer than normal lately?
2025 averaged 59.7°F, 0.7°F below the 1991-2020 normal of 60.4°F. 2 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 60.0°F | −0.4°F | 39.16 | 0.0 |
| 2022 | 60.0°F | −0.4°F | 48.53 | 2.8 |
| 2023 | 60.6°F | +0.2°F | 48.03 | 0.0 |
| 2024 | 60.7°F | +0.3°F | 54.29 | 0.0 |
| 2025 | 59.7°F | −0.7°F | 44.39 | 0.0 |
Over 61 complete years from 1950 to 2025, the station's annual mean temperature rose at a fitted 0.7°F per century (+0.04°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00388786; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Union's climate compare?
Union is warmer than 5 of the other 72 places with their own NOAA record in South Carolina, and wetter than 8. Across the 7,247 U.S. stations with normals, its annual mean of 60.4°F is warmer than 76%.
In the Köppen classification computed from these normals, Union 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 Union share this climate record?
3 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.
- Whitmire, SC1,439 people · 8 mi S
- Buffalo, SC1,232 people · 8 mi N
- Cross Anchor, SC89 people · 11 mi W
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 Union's climate
What is the coldest month in Union?
January, with a normal high of 53°F and a normal low of 29°F. The warmest is July (90°F by day, 68°F at night).
Does it snow in Union?
Yes: 2 inches in a normal year, falling on 1 days with 0.1 inch or more, the most in January (0.9 inches).
What is the rainiest month in Union?
March, with 4.29 in of precipitation in a normal year; the driest is May with 3.13 in.
What plant hardiness zone is Union in?
The USDA's 2023 map puts Union in zone 8a in ZIP code 29379, the nearest ZIP area. By the same method at Union's NOAA station, the coldest night of a typical year reaches 10°F (21 years, 1991-2020): zone 8a.
How late can frost come in Union?
In half of years the last 32°F night comes after April 6; in one year in ten it comes after April 21. Waiting until April 21 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
- Santuck, SC8 miles from this station, 61.7°F a year
- Clinton, SC16 miles from this station, 61.8°F a year
- Laurens, SC22 miles from this station, 61.2°F a year
- Newberry, SC22 miles from this station, 61.8°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made