Koster weather in December

In December, Koster sees average daytime highs of 28°C and overnight lows near 17°C, with 121 mm of rain across 14.8 wet days and about 13.6 hours of daylight. It is the 2nd-warmest and 1st-wettest month of the year here.

Day-to-day highs hold fairly steady near 28°C through the month. The sky is clear or mostly clear about 35% of the time in December, and the air most often feels comfortable.

Daylight stretches from about 13 h 30 min at the start of December to 13 h 36 min by month's end. Set against the rest of the year, December is Koster's 12th-clearest and 5th-windiest month. For the whole year in context, see Koster's year-round climate.

Daytime high
28°
2nd warmest
Overnight low
17°
10th coldest
Rainfall
121 mm
14.8 wet days
Daylight
13 h 36 min
5:20 AM – 6:57 PM
Cloud cover
55%
12th clearest
Wind
9 km/h
5th windiest
Solar energy
6.8 kWh/m²
Travel score
5.5
out of 10

Koster is place in North West, South Africa.

Founded
1860

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in December

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 28°C through the month.

A typical December day in Koster reaches about 28°C in the afternoon and slips back to 17°C overnight — a 11°C spread between the day's warmth and the night's chill. On most days the high lands between 23°C and 33°C. Set against its neighbours, December runs on par with November and on par with January.

10°15°20°25°30°35°151015202531
Avg high (°C)Avg low (°C)
12817
22817
32817
42817
52817
62817
72817
82817
92817
102817
112817
122817
132817
142817
152817
162818
172818
182818
192818
202818
212818
222818
232818
242818
252818
262818
272818
282818
292818
302818
312818

Koster weather by month

How December compares with the rest of the year at a glance. December is the 2nd-warmest and 1st-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan28° / 18°9814.413.45.5
Feb28° / 18°9612.312.95.9
Mar27° / 16°7611.112.26.7
Apr24° / 13°366.511.47.8
May22° / 182.210.88.7
Jun20° / 81.210.48.4
Jul20° / 30.510.58.5
Aug23° / 81.411.19.0
Sep26° / 12°142.211.88.5
Oct28° / 15°527.812.67.0
Nov28° / 16°7812.113.35.9
Dec28° / 17°12114.813.65.5

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 35% of the time in December, the cloudiest month of the year.

Beyond those clear spells, partly cloudy skies cover about 25% of December, with mostly cloudy or overcast conditions the remaining 41%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
15941
25842
35842
45743
55743
65842
75842
85941
95941
106040
116040
126040
136040
146139
156139
166139
176139
186238
196139
206139
216040
226040
235941
245941
255842
265842
275842
285941
296040
306040
316040

Chance of precipitation in December

Any precipitation

Koster gets around 121 mm of rain over 14.8 wet days in December, the wettest month. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 47% and peaks near 49% on the wettest days.

0%20%40%60%151015202531
Rain chance (%)
148
248
349
449
549
649
749
849
948
1048
1148
1247
1347
1447
1547
1646
1746
1846
1946
2046
2146
2246
2347
2447
2547
2646
2746
2846
2945
3045
3145

Humidity in December

DryComfortableHumidMuggyOppressiveMiserable

Most of December feels comfortable — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, December lands in the comfortable band about 42% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)
14038220
23939220
33840220
43641230
53542230
63343240
73244240
83144240
93045250
102945250
112846251
122746261
132647261
142647271
152547271
162447281
172347281
182347291
192246312
202145322
212144332
222043352
231942363
241940383
251839393
261838403
271838414
281837424
291736424
301736434
311736435

Wind in December

Winds average 9 km/h in December.

Across December, daily wind ranges from about 9 km/h on the calmest days to 10 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202531
Wind speed (km/h)Feels
110calm
210calm
310calm
410calm
510calm
610calm
710calm
810calm
910calm
1010calm
1110calm
1210calm
1310calm
149calm
159calm
169calm
179calm
189calm
199calm
209calm
219calm
229calm
239calm
249calm
259calm
269calm
279calm
289calm
299calm
309calm
319calm

Sunrise & sunset in December

DaylightNight

Daylight runs from about 13 h 30 min at the start of December to 13 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 6 minutes over December. Sunrise moves from 5:17 AM to 5:28 AM, and sunset from 6:47 PM to 7:03 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
113.55:176:47
213.55:176:48
313.55:176:49
413.55:176:49
513.55:186:50
613.55:186:51
713.65:186:51
813.65:186:52
913.65:186:53
1013.65:186:53
1113.65:196:54
1213.65:196:54
1313.65:196:55
1413.65:206:56
1513.65:206:56
1613.65:206:57
1713.65:216:57
1813.65:216:58
1913.65:226:58
2013.65:226:59
2113.65:226:59
2213.65:237:00
2313.65:237:00
2413.65:247:01
2513.65:247:01
2613.65:257:02
2713.65:257:02
2813.65:267:02
2913.65:277:03
3013.65:277:03
3113.65:287:03

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 6.8 kWh/m² — the sunniest month for solar.

For context, solar energy here swings from a low near 3.91 kWh/m² to a high of 6.8 kWh/m² in December across the year — December's 6.8 kWh/m² sits near the top of that range.

0246151015202531
Solar energy (kWh/m²)Level
16.7Intense
26.7Intense
36.7Intense
46.7Intense
56.7Intense
66.7Intense
76.7Intense
86.7Intense
96.8Intense
106.8Intense
116.8Intense
126.8Intense
136.8Intense
146.8Intense
156.9Intense
166.9Intense
176.9Intense
186.9Intense
196.9Intense
206.9Intense
216.9Intense
226.9Intense
236.9Intense
246.9Intense
256.9Intense
266.9Intense
276.9Intense
286.8Intense
296.8Intense
306.8Intense
316.8Intense
Planning a trip in December

Hazard calendar for Koster

In seasonPeak

In December, Koster sits inside its rainy season season. The full year is below, with each hazard's peak months called out.

Koster's rainy season runs November–March, when most of the year's rain falls.

Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is December a good time to visit Koster?

Our two travel scores rate December for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

5.5
Sightseeing
11th-best month of the year
6.2
Beach & pool
9th-best month of the year

December is a reasonable time to visit Koster for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Koster in December

From December's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In December, Koster sees daytime highs around 28°C and nights near 17°C. Pack light clothes, rain gear and sun protection. About 15 days see rain.

light clothesrain gearsun protection

UV index in Koster in December

LowModerateHighVery highExtreme

Clear-sky midday UV in December peaks around 14 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Koster peaks around January 13 at about 15 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near June 19 at about 5 (high).

The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeVery highHighVery highExtremeJan 13UV 15Jun 19UV 5
UV index (midday)Level
Jan15Extreme
Feb13Extreme
Mar12Extreme
Apr9Very high
May6High
Jun5High
Jul6High
Aug8Very high
Sep9Very high
Oct11Extreme
Nov12Extreme
Dec14Extreme

Air quality in Koster in December

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where December falls, not just the annual average.

Air quality in Koster is worst in June — around 69 µg/m³ PM2.5 (unhealthy), about 5.0× the cleanest month (December, 14 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

020406080JanFebMarAprMayJunJulAugSepOctNovDecModeratePoorUnhealthyPoorModerateJun 1869 µg/m³Dec 2114 µg/m³
PM2.5 (µg/m³)Level
Jan15Moderate
Feb22Moderate
Mar31Moderate
Apr46Poor
May62Unhealthy
Jun69Unhealthy
Jul66Unhealthy
Aug53Poor
Sep47Poor
Oct28Moderate
Nov17Moderate
Dec14Moderate
Location & terrain

Where is Koster?

Koster sits at 25.9°S, 26.9°E, 1,620 m above sea level, in South Africa. The nearest listed city is Rustenburg, 41 km away.

Topography around Koster

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Koster.

Within 3 km, the terrain around Koster has only modest variations in elevation — a maximum elevation change of 168 m around an average of 1,581 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 397 m; within 80 km, large variations in elevation — a maximum elevation change of 868 m.

The land around Koster is covered by grassland (50%) and cropland (31%) within 3 km, grassland (54%) and cropland (26%) within 16 km, and grassland (58%) within 80 km.

3 km
168 m
16 km
397 m
80 km
868 m
treesshrubsgrasslandcroplandartificial surfaces
December weather nearby: Rustenburg 41 km · Ventersdorp 51 km · Marikana 61 km · Carletonville 75 km · Hartbeestfontein-A 77 km · Coligny 78 km · Bagale 78 km · Lichtenburg 80 km

South Africa travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type C / M / N
230 V · 50 Hz
Prices
≈ 41% of US
price level, 2025
GDP per capita
$6,598
2025
Happiness
5.0 / 10
World Happiness, 2025
Safe drinking water
68%
of population, 2024
Homicide rate
43.7
per 100k, 2022
Road deaths
22.2
per 100k/yr, 2019
Income group
Upper middle
World Bank
English
Very high
EF EPI 602
Religion
Christian 86%or other traditional African religions 5%nothing in particular 5%Muslim 2%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Koster (-25.863°, 26.8976°, elevation 1,620 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).