The South African Weather Service has issued weather warnings for KwaZulu-Natal, Gauteng, Mpumalanga and Limpopo for Monday.
The forecaster said isolated to scattered showers and thunderstorms are expected over the province of KZN.
"Some of these thunderstorms are expected to become severe over most parts of KZN, except the north-eastern parts and may be accompanied by large amounts of small hail," Saws said.
It added that there could also be damaging winds, excessive lightning and heavy downpours.
A severe thunderstorm warning is also expected over Gauteng, the Highveld escarpment of Mpumalanga and over the south-western Bushveld of Limpopo in the afternoon and evening.
Saws warned of heavy downpours, large amount of small hail and gusty winds.
"Extremely high fire danger conditions are expected over the southern parts of the ZF Mgcawu and the western parts of the Pixey Ka Seme District Municipalities in the Northern Cape as well as in places in the Limpopo Valley and the southern parts of the Limpopo Lowveld," Saws added.
Meanwhile, a heat wave with persistently high temperatures is expected in the north-western and north-eastern parts of KZN.
Saws warned that this is expected to continue until Wednesday.
"Extremely uncomfortable conditions are expected along the coast and adjacent interior of KZN, the Lowveld of Mpumalanga and Limpopo, as well as the Limpopo Valley until Wednesday," the forecaster predicted.
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