Koster in Summer
In summer (December, January and February), Koster sees average daytime highs around 28°C and overnight lows near 18°C, with 315 mm of rain over about 42 wet days across the season. It is the warmest season of the year and the wettest season of the year.
Across summer, daytime highs hold fairly steady around 28°C. The sky is clear or mostly clear about 38% of the time across summer, and the air most often feels humid.
Summer is Koster's weakest season of the year to visit on our travel score. For the whole year in context, see Koster's year-round climate.
- Avg daytime high
- 28°C
- warmest season of the year
- Avg overnight low
- 18°C
- Rainfall
- 315 mm
- 42 wet days
- Avg wind
- 9 km/h
- Travel score
- 5.6
- weakest season of the year
- Months
- Dec · Jan · Feb
Temperature in Koster in Summer
Across summer, daytime highs hold fairly steady around 28°C.
A typical summer day in Koster reaches about 28°C and drops to 18°C overnight. The warmest of the three months is January, the coolest December.
Koster weather by month
How the three summer months (December, January and February) compare with the rest of the year — the season's months are highlighted.
| Month | High / Low (°C) | Rainfall (mm) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 28° / 18° | 98 | 14.4 | 13.4 | 5.5 |
| Feb | 28° / 18° | 96 | 12.3 | 12.9 | 5.9 |
| Mar | 27° / 16° | 76 | 11.1 | 12.2 | 6.7 |
| Apr | 24° / 13° | 36 | 6.5 | 11.4 | 7.8 |
| May | 22° / 9° | 18 | 2.2 | 10.8 | 8.7 |
| Jun | 20° / 6° | 8 | 1.2 | 10.4 | 8.4 |
| Jul | 20° / 5° | 3 | 0.5 | 10.5 | 8.5 |
| Aug | 23° / 8° | 8 | 1.4 | 11.1 | 9.0 |
| Sep | 26° / 12° | 14 | 2.2 | 11.8 | 8.5 |
| Oct | 28° / 15° | 52 | 7.8 | 12.6 | 7.0 |
| Nov | 28° / 16° | 78 | 12.1 | 13.3 | 5.9 |
| Dec | 28° / 17° | 121 | 14.8 | 13.6 | 5.5 |
Cloud cover in Summer
The sky is clear or mostly clear about 38% of the time across summer.
Chance of precipitation in Summer
Koster gets around 315 mm of rain over 42 wet days across summer. The line is the day-by-day chance of measurable precipitation.
Humidity in Summer
Most of summer feels humid — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Summer
Winds average 9 km/h across summer.
Sunrise & sunset in Summer
Daylight runs from about 13 h 30 min in early December to 12 h 36 min by late February. The lit band spans sunrise to sunset each day.
Solar energy in Summer
Average shortwave solar energy reaching the ground each day across summer, about 6.6 kWh/m².
Hazard calendar for Koster
In summer, Koster overlaps 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.
Is summer a good time to visit Koster?
Our two travel scores rate summer for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
summer 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 Summer
From summer's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In summer, Koster sees daytime highs around 28°C and nights near 18°C. Pack light clothes, rain gear and sun protection. About 42 days see rain.
UV index in Koster in Summer
Clear-sky midday UV across summer averages 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.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 15 | 13 | 12 | 9 | 6 | 5 | 6 | 8 | 9 | 11 | 12 | 14 |
| Level | Extreme | Extreme | Extreme | Very high | High | High | High | Very high | Very high | Extreme | Extreme | Extreme |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 15 | Extreme |
| Feb | 13 | Extreme |
| Mar | 12 | Extreme |
| Apr | 9 | Very high |
| May | 6 | High |
| Jun | 5 | High |
| Jul | 6 | High |
| Aug | 8 | Very high |
| Sep | 9 | Very high |
| Oct | 11 | Extreme |
| Nov | 12 | Extreme |
| Dec | 14 | Extreme |
Air quality in Koster in Summer
Average fine-particle pollution (PM2.5) through the year — so you can see where summer 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).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 15 | 22 | 31 | 46 | 62 | 69 | 66 | 53 | 47 | 28 | 17 | 14 |
| Level | Moderate | Moderate | Moderate | Poor | Unhealthy | Unhealthy | Unhealthy | Poor | Poor | Moderate | Moderate | Moderate |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 15 | Moderate |
| Feb | 22 | Moderate |
| Mar | 31 | Moderate |
| Apr | 46 | Poor |
| May | 62 | Unhealthy |
| Jun | 69 | Unhealthy |
| Jul | 66 | Unhealthy |
| Aug | 53 | Poor |
| Sep | 47 | Poor |
| Oct | 28 | Moderate |
| Nov | 17 | Moderate |
| Dec | 14 | Moderate |
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.
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
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.