5 September 2023
By: Alani Janeke
The winter rainfall region can expect weekly rain until early October due to regular cold fronts. The risk of frost in the interior is also high.
The first signs of spring are visible but weather models indicate that cold fronts will continue to affect South Africa from the south-west in the coming weeks, with winter rain persisting until at least the first week of October.
“Rain is possible in almost every week of September, as well as the first week of October. Along with that, very cloudy conditions will prevail,” says Johan van den Berg, an independent agricultural meteorologist.
When cold fronts arrive, extremely low minimum temperatures will occur in the Winelands, the Overberg and the Southern Cape.
“Minimum temperatures below 0°C are possible, especially on September 10 and 11, in places such as Caledon, Robertson, Swellendam, Paarl and Ceres,” says Ven den Berg.
“Particularly, the southern parts of the Langkloof are also at risk of frost damage, especially on September 10 and 11. Snow may fall in the Ceres area on September 6, as well as on September 10 and 11.”
Van den Berg says the low temperatures have significant implications for the winter grain industry, as most grains are in a sensitive reproductive stage. They may also damage early developing fruits and grapes.
“This is a very significant risk that can have a major impact on yields, especially given the good yield potential with very good water conditions,” he says.
Frost and fires in the interior
In the summer rainfall region, the cold fronts are expected to move quickly. Cold conditions with frost are possible on September 6 and 7 in the central to southern interior, followed by high temperatures from September 8 to 10.
There may be sharp temperature drops when a cold front moves over the country from September 11 to 15. Lower temperatures are also possible from September 22 to 25. At this early stage, weather models also indicate temperature drops in the first week of October.
“The areas in the summer rainfall region where the risk is greatest are the Northern Cape, especially the lower Orange River region, the western parts of North West like Vryburg, the entire Free State, the southern parts of KwaZulu-Natal like Kokstad, as well as most of the Eastern Cape.”
Van den Berg says this pattern is typical of El Niño seasons such as those of 2015-16 and 2018-19, when frost occurred until October.
“Management measures to prevent frost damage so late in the season are very limited, especially on large farms. While the creation of smoke clouds over a farm, the use of wind machines and helicopters to mix the air, and other measures can be applied, they are not very effective,” says Van den Berg.
“During these brief sharp temperature drops, it is advantageous for plant leaves not to be wet, and it is preferable not to wet them overhead on the day when frost is expected.”
High fire danger
With cold fronts moving across the country and little rain, fire danger remains high over most of the summer rainfall region. The regular cold fronts will bring regular northerly and westerly winds of up to 60 km/h in the interior in the coming weeks.
“If lightning begins to occur, it can also greatly increase the risk.”
One of the management measures Van den Berg suggests is to limit damage to livestock and property by using camps with lower fire risk and farms that are more easily accessible as safe havens. “Warn everyone on the farm against open fires and clean areas around property with tools.”
