- Average annual rainfall (low): 150 mm
- Average annual rainfall (high): 321 mm
- Average day temp summer: 28.6 d C
- Average night temp summer: 14.1 d C
- Average day temp winter: 21.1 d C
- Average night temp winter: 7.4 d C (Infruitec Nietvoorbij)
The annual rainfall in the Robertson Wine Valley is approximately 260 mm per annum of which ± 70 % falls during winter. This rain is not enough and therefore additional irrigation is necessary for growing wine grapes. The Robertson Wine Valley growers can be divided into two main groups of water users:
- Growers depending on the Breede River and Brandvlei Dam as their main source of irrigation water. By far the highest percentage of growers will fall into this group. Winter water from the rivers from the adjacent Du Toitskloof mountain range is stored in the Brandvlei Dam near Worcester. Some water from the Breede River is also pumped into the Brandvlei Dam. During the beginning of the irrigation season (September to beginning of November) the Breede River normally has sufficient water to supply the network of irrigation canals supplying water to growers. From November the irrigation demand gets to high and additional water from the Brandvlei Dam is released into the Breede River system to sufficiently supply the irrigation canals. The growers have a water allocation from the canals which they then store in dams from which they then irrigate their vineyards and orchards.
- Growers depending on stored winter water and boreholes Towards the mountains and further away from the Breede River growers do not have the luxury of irrigation canals from the Breede River and therefore these growers need to store winter run-off water from the mountain in storage dams on their properties. Quite a number of these growers are also dependent on additional groundwater extracted from boreholes.