The South African Weather Service has warned Gauteng residents to be extra cautious as it predicts thunderstorms and heavy downpours for Thursday.
It said conditions remained very favourable for first real storms of the new season in the City of Johannesburg, as well as parts of Tshwane and Ekurhuleni.
Forecaster Edward Engelbrecht said: “Large hail, strong winds and heavy rain are expected at this time of year. We will see more thunderstorms at this time of year.”
The rain comes as Gauteng residents have been urged to use water sparingly.
The Department of Water and Sanitation said dam levels in the Vaal River were much lower than they were this time last year.
Maintenance under way at the Lesotho Highlands Water Project tunnel system is also contributing to the shortages.
The City of Johannesburg announced on social media that no water transfers to the dam would be possible until 30 November due to maintenance.
According to the Rand Water website, the Vaal Dam is 53% full.