JOHANNESBURG (Reuters) - Unusually heavy late summer rains have killed more than 30 people in South Africa but have brought welcome relief to grain farmers after drought conditions in some parts of the maize belt in January and February.

The government said 32 people had died because of the rains over the past two weeks in the northern and eastern provinces of North West, Limpopo, Mpumalanga, Gauteng and KwaZulu-Natal. The toll included 25 drownings and six people killed by lightning.

"A number of people have been rescued from the roofs of their vehicles and several were trapped in their homes. Rescue and search services remain on high alert," it said in a statement.

However, the rains have broken a drought in parts of North West province and have been welcomed by farmers in Africa's top maize producer.

"The grain farmers welcome the rain. The crops planted late will benefit from the rain. There is relatively very little damage so far," said Jannie de Villiers, the chief executive of Grain SA, which represents grain farmers.

Some farmers in eastern Mpumalanga province had reported that secondary roads had been damaged and it might be difficult to get the crops to silos as a result, De Villiers added.

South Africa is likely to harvest 12.403 million tons of maize in 2014 after reaping 11.69 million tons last year, the government's Crop Estimates Committee (CEC) says.

Maize is the staple crop in South Africa and a poor harvest can push overall inflation much higher.

Maize futures for the most-traded July contract hit record highs around 2,500 rand a ton in January but have since fallen 16 percent to 2,080 rand a ton in response to the rains.

The wet weather also damaged coal supplies used to fuel power stations in Mpumalanga, forcing state-run power utility this month to impose the first rolling blackouts since 2008 to prevent a collapse of the national grid.

(Reporting by Ed Stoddard and Olivia Kumwenda-Mtambo; Editing by Ed Cropley)