The reserve is situated in the western part of the temperate winter rainfall region that has a Mediterranean climate.
The mean annual rainfall is approximately 930.6mm over a 12 year period (1988-99 at Base Camp) and 602.9mm over a 51 year period (1947-98) measured at the Magnetic Observatory in Hermanus.
Of significant interest is the added 300mm that falls in Vogelgat in comparison to Hermanus town itself which is only 10km west of Vogelgat.
Mean annual precipitation:
598mm to 1238mm -1988-99 (Wardens records, Base Camp)
906mm to 1473.5mm -1981-99 (Quark House)
361.4mm to 909mm- 1947-98 (Magnetic Observatory Hermanus)
There is a second rainfall gauge at Quark House, which is situated in the centre of the reserve and at an altitude of 360m.
The mean annual rainfall 1981-99 is 1 214.5mm, nearly 300mm more rainfall than measured at Base Camp.
Rainfall is usually of low intensity, but can continue for 8 days. Thunderstorms have a frequency of less than 5 days per annum.
The higher peaks of the reserve are often covered in cloud, and it has been estimated that over 500mm per annum can be precipitated from these clouds without being recorded in the rain gauge.
The maximum mean occurring in June (115mm) and the minimum in January (37mm).]
Wettest 3 months.
May, June, July (9.8% to 12% of MAP per month; Base Camp)
The wettest month recorded was 236.7mm in September 1951.
Driest 3 months
December, January, February (4% to 5.8% of MAP per month; Base Camp)
The driest month recorded was 0.0mm in January 1976.
Rainfall fairly evenly distributed over the year (6.8% to 12% of MAP per month; Base Camp)
Has been recorded (1995) within the reserve at Beacon Hut. A second occurrence has been witnessed Hauman pers com. Hail does occur occasionally.
In August 2003 unprecedented snowfalls fell.
The heaviest in 60 years.
Precipitation in the form of mist
Occurs in autumn and winter. At times the whole of the Overberg can be covered in a thick mist bank.
Absolute Maximum Temperature
Mean average: 28.7ºC.
(Mean 1962-98 Hermanus Magnetic Observatory)
Absolute Minimum Temperature
Mean average: 7.5ºC
(mean 1962-98 Hermanus Magnetic Observatory)
(See Appendix VII)
January and February: 31.8ºC. (Mean 1962-1998) The hottest temperature recorded was 37.3ºC in 1975 February 18th.
The months of December (30.7ºC), January (31.8ºC), February (31.8ºC) and March (30.9ºC) are the warmest months.
July: 3.6ºC. The three coldest months are June (4.0ºC), July (3.6ºC) and August (4.1ºC). The coldest day recorded was 1.5ºC on 9th July 1982.
The wind cycle falls into the bimodal wind regime.
Predominant winds in are summer are from the east south east to south east sector with an average velocity of 35km/h,
due to the South Atlantic high pressure system.
In winter predominant winds are from north west and west north west sectors.
Winds speeds may reach 60km/h or more at times.
Wind from the south east sector occur for 32% of the time and from the north west sector occur 28% of the time.
The Klein River Mountains have localised influence on wind direction.
A characteristic of the winter months is the occurrence of hot, dry winds coming from the interior, locally known as “Berg winds”. These winds can lead to an increase in temperatures of over 10ºC within a few hours.
Berg winds often coincide with the passing of cold fronts.
These winds result in very warm days experienced during winter.
Drainage region : South-western Cape
Number of rivers flowing through the reserve : One: The Vogelgat River.
This river used to supply water to Hermanus. Figures gathered during the 1940’s suggest that 750m² water per day were gravity fed into the reservoir in Voelklip for potable water for the town of Hermanus.
Vogelgat River Catchment area : 7.2km²
Highest and lowest elevations on the reserve: 0 – 820m (Beacon)
Number of named seasonal streams on the reserve
Beacon Head Stream
Black Rock Stream
Gum Tree Stream
Lone Tree Stream
Roads End Stream
Number of named basins
Shepherd’s Hill Marsh
Natural pools named
Two Pole Pool