Very low temperatures predicted for the rest of August

15 August 2023

By: Alani Janeke

The mercury will drop sharply in the last 10 days of August, while cold fronts could still cause snow.

Amid low minimum temperatures and intermittent frost over the central and southern interior, temperatures have generally started to rise over the past few weeks.

“Solar energy reaching the Earth’s surface on clear days has increased by about 20% from midwinter in June to mid-August,” says Johan van den Berg, an independent agricultural meteorologist. 

“This period, where daytime temperatures rise quickly, stimulates growth and plant development. This exposes sensitive plant tissue to the atmosphere. It’s also the time with the most frost damage.”

Chance of frost

August is generally the third coldest month, after June and July. Although temperatures show a rising trend, very cold conditions can still occur. 

“Weather models indicate that this will be the case this year in the latter part of August,” says Van den Berg. “There are still several cold fronts moving in from the south-west across the country, causing rain over the winter rainfall area while importing cold air over the interior.”

Van den Berg says minimum temperatures will drop as low as -6°C in the last 10 days of August in Molteno, -5°C in Barkly East, -4°C in Bloemfontein and 0°C in Prieska. Temperature drops will also occur further north by August 25, but frost is not expected in the northern provinces. 

In Windhoek, Namibia, minimum temperatures will drop below 5°C in the last week of August, although daytime temperatures will be around 30°C.

“There is a high risk of further cold conditions and frost before the end of August over the Northern Cape, the southern parts of Namibia, North West, the Free State, the southern parts of Mpumalanga, the south-western parts of KwaZulu-Natal, the Eastern Cape, and the northern parts of the Western Cape,” says Van den Berg.

During the previous El Niño system in 2019, frost occurred in the central to western interior as late as October 30, causing hundreds of millions of rand in damage to wheat, pecan nuts and grapes. 

“Cold fronts won’t suddenly stop moving over the country as spring arrives. Further cold conditions are also expected in September and perhaps even October,” says Van den Berg.

Snow in August

He says there is a chance of snow over the Eastern Cape and the Drakensberg on August 23 and 28. “August is known for regular snow, but it can also occur sporadically later in the year. The latest recorded occurrence of snow was on December 6 and 7, 1970, when it snowed as far as the eastern Free State and KZN.”

Rain

Regarding rain in the winter rainfall region, fairly good precipitation is expected on August 17 and 18, August 21 and 22, August 24 and 25, and September 2 and 3, especially over the winelands and the Cape metropole. 

Rainfall of up to 25mm is possible over the Swartland on August 24 and 25, and September 2 and 3. Less rain is expected further along the West Coast, the adjacent interior, the Karoo, and the south coast of the Western Cape.

With the presence of the El Niño system, average to above-average rainfall over the region is expected to continue in September and October.

As for the summer rainfall region, very little or no rain is expected for the rest of August, with the exception of light precipitation over the Eastern Cape, the southern parts of the Free State, Lesotho, and the coastal areas of KZN.

“However, it appears that conditions for rain will improve in the second half of September over large parts of the country.”