The climatic diversity of the Breede River valley, akin to a Mediterranean climate, influences the Seven Sisters wines with summers being hot and dry. Temeratures averaging 30°C, sometimes peaking at 40°C on the hottest of days, makes irrigation essential. Winters are generally colder than in the Western Cape’s more coastal regions, allowing the vines to achieve proper dormancy. Rainfall is largely contained to the cold winter months, when vines are dormant and can store up resources for the growing season. The average annual precipitation is generally below 400 millimetres (15.75 in).
Soil types are varied. Surrounding the river, they are mainly alluvial, with some sandy loam. Higher in the mountains, they are more rocky and stony. Shale and sandstone are dominant in Worcester, while Robertson’s red, gravelly soils benefit from pockets of limestone, which add a chalky minerality to the vines grown there.