28 November 2023
Weather predictions suggest good rain showers from the second week of December in areas that still need to do plantings, but high temperatures may persist until then.
Heatwave conditions over large parts of South Africa may persist until the second week of December when the chance of rain slightly improves. The heatwave has been caused by the Atlantic high-pressure system, resulting in a dome of high pressure over Southern Africa.
Johan van den Berg, an independent agricultural meteorologist, says a high-pressure system causes descending air with warm and dry conditions. As the position of the system has changed slightly, it has allowed a weaker low-pressure system to develop over northern Namibia, bringing rain there.
The system has dampened rain conditions further south, except over the east coast and adjacent inland areas of South Africa, where there have been showers.
“It seems these conditions will persist, although the chance of rain is slightly better in the second week of December,” says Van den Berg
The big issue is whether there will be enough rain to allow plantings in the western production areas. “Plantings of maize must be done by the end of December. It is estimated that less than 10% of the expected plantings west of the N1 have been done, with more than 80% completed roughly east of the N1,” says Van den Berg.
“This means only about 30% to 35% of the total expected maize plantings for South Africa have been done to date. Almost no groundnuts (which should be planted before the end of November) have been established yet.”
Will there be enough rainfall?
Although rain is expected in the second week of December, it is uncertain whether there will be enough for plantings. “The problem is that with the very warm conditions, more than 30 mm and in many cases more than 40 mm are needed to saturate the soil,” says Van den Berg.
“Currently, it is predicted that rain plantings can be done, but generally marginal amounts of rain will occur in at least the next two weeks.
“Therefore, the risk that all plantings may not be done in time is increasing. Producers will also have to prepare to possibly do plantings over the festive season.”
During the previous strong El Niño system of 2015-16, the first good rains of more than 30 mm occurred only in the first two weeks of January 2016 in places such as Bothaville and Lichtenburg. “This can create a dilemma for maize producers again this year if that is the case because it is technically too late to plant and there is a very high risk of frost damage in April if early frost occurs.”
More heat to come
In the Northern Cape, temperatures above 40°C are expected until about December 1, with temperatures above 35°C predicted for most of December. These warm and dry conditions are favourable for the grape industry, with a reasonably large harvest expected this year. The industry may be under pressure to harvest and/or process the grapes quickly because ripening will occur faster.
Very high temperatures will also occur over the central to northern and northwestern parts of the country (North West, Gauteng, Limpopo and the western Free State) until about December 5, when there is a possibility of light rain.
Moderate to cooler conditions may set in from November 29 over Mpumalanga, the eastern Free State, KwaZulu-Natal and the Eastern Cape, although high temperatures may sporadically occur in inland Eastern Cape areas such as Cradock, Graaff-Reinet, Aliwal North and Middelburg.
Shorter periods of very warm conditions of 40°C or higher are possible in the next two weeks over western parts of the Western Cape, such as Vredendal and Clanwilliam, as well as northern inland areas of the Western Cape, such as Beaufort West and Laingsburg, warns Van den Berg.
Variable temperatures are predicted over the rest of the winter rainfall area. Cooler conditions with only one or two days of very warm conditions are predicted over the Garden Route from Mossel Bay to as far as the northern coastal areas of the Eastern Cape and the southern parts of KwaZulu-Natal.
The current very warm conditions are probably not the last this season because the warmest months are still ahead. During the 2015-16 summer, maximum temperatures in Bothaville were about 4°C warmer than normal for December 2015. In the first 10 days of January 2016, it was about 6°C warmer than normal, and the average for February was almost 3°C warmer.
Van den Berg says from November 1, 2015, to February 29, 2016, there were only 22 days where the maximum temperature was not above 30°C in Bothaville. This is an indication of what is possible regarding heat conditions during El Niño seasons.
