Climate Insights for Koster

The climate in Koster is temperate. The average annual temperature is 18°C and approximately 621mm of precipitation falls per year. December is the wettest month, receiving around 119mm of rainfall. Koster is in the Southern Hemisphere. The seasons are reversed — summer runs from December to February, while winter falls between June and August. The summer months are: November, December, October. The coldest months are July, June, August, when temperatures can drop to 4°C.

Temperatures in Koster vary considerably across the year, with a 24°C difference between the coldest and warmest months. The warmest month is November, when average highs reach 28°C and the mean temperature sits around 21°C. July is the coolest month, with minimum temperatures around 4°C and an average of 11°C. On average, daily temperatures fluctuate by about 13°C between overnight lows and afternoon highs. The sharpest temperature change occurs between August and September, with a 4°C shift in average temperatures.

Koster is a relatively dry area, receiving approximately 621mm of precipitation annually, which averages out to around 52mm per month. The wettest month is December, averaging 119mm of rainfall. January and February also tend to see above-average precipitation. The driest month is August, with just 2mm. That's 117mm less than December, the wettest month. Rainfall is heavily concentrated in certain months, creating a distinct wet and dry season. Visitors should plan around these patterns, as the difference between peak and low months is dramatic.

Koster is mildly breezy, with an average annual wind speed of 18km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is November, averaging 21km/h, noticeable enough to affect lighter outdoor activities. The calmest conditions occur in May, with average winds dropping to 15km/h, making it an ideal period for wind-sensitive activities. There is moderate seasonal variation in wind speed, with a 6km/h gap between the calmest and windiest months.

It is currently autumn in Koster, which began on March 20, 2026. Koster is in the Southern Hemisphere, where the seasons are reversed — spring starts in September, summer in December, autumn in March, and winter in June. The warmest period peaks in November at around 28°C, while the coldest stretch bottoms out in July near 4°C. Winter is next, beginning on June 21, 2026 — 89 days from now.

The best time to visit Koster is during March, April, September, October and November, when the weather is most comfortable for travellers. During these months, average temperatures hover around 19°C with modest rainfall averaging 50mm per month. By contrast, July can be quite cold with temperatures dropping to 4°C. A light rain jacket is recommended, though showers are generally brief and shouldn't disrupt your plans.

The table below shows monthly climate averages for Koster based on historical weather data. Min and max temperatures represent typical overnight lows and afternoon highs for each month, shown in degrees Celsius (°C). Precipitation is measured in millimetres (mm) and indicates the average total rainfall per month. Wind speed is the average sustained speed in kilometres per hour (km/h). All values are based on averages from over 10 years of historical weather data. The current month is highlighted for quick reference.