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General Information on the Vaal

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The Vaal Triangle is located south of the city of Johannesburg, in the interior high-plateau of South Africa known as the Highveld.  Due to it’s height above sea-level (the city of Vereeniging is approximately 1580 m above sea level), the Vaal Triangle enjoys beautiful warm to hot sunny days in the Spring and Summer with temperatures often reaching 30 to 35ºC.  This is also the rainy season (October to April) when spectacular thunderstorms can be seen.  The Winter season tends to be dry with crisp cold mornings (frost in June and July), although the days are warm and sunny.  The Highveld climate - with most days enjoying up to ten hours per day of sunshine - is considered one of the best in the world.
 
The average annual rainfall is 638 mm.  However, the erratic nature of rainfall leads to a high probability of droughts (defined as 21 days with less than 25mm of rain).  December has the lowest drought probability of 37%.
 
The prevailing winds throughout most of the year are north-westerly and north-easterly due to the anticyclonic circulation.  During winter, particularly July and August, south-westerly winds blow more frequently because of the changing weather conditions (the northward shift of the high pressure belt and enhanced influence of westerly wave disturbances e.g. cold fronts).  Summer months are characterised by the weakening and southward shift of the anticyclonic belt, which allows tropical easterly flow to resume its influence over the region.  North-easterly winds increase during summer (December to February) and north-westerly winds and northerly airflows continue.

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