* KwaZulu Natal province in throes of worst drought since 1900

* Drought threatens maize crop, may fuel inflation

* Weather presents political challenge to ruling ANC

By Ed Stoddard

JOHANNESBURG, Nov 10 (Reuters) - The sugar-growing South African province of KwaZulu Natal is the driest it has been in over a century, according to data provided on Tuesday by the South African Weather Service, underscoring the scale of a drought scorching Africa's most advanced economy.

The drought, seen worsening due to an El Nino weather pattern, threatens South Africa's diverse farm sector including its key maize crop, which may fuel food prices and inflation at a time when the central bank is in a tightening cycle.

For South Africa as a whole, the low rainfall and rolling heatwaves that have marked the start of this summer come on the heels of 2014-15, which was the driest season since 1991-92, according to the data provided to Reuters.

In KwaZulu Natal province, a key political base for the ruling African National Congress (ANC) and a major sugar-growing region, the 2014/15 season was the driest since at least 1900.

The Weather Service measures seasonal rainfall by the southern hemisphere summer, so has not yet made a call about the severity of the current season.

"We are currently at the beginning of the summer season ... We do not exactly know how the current season would turn out," the Weather Service said in an emailed response to queries from Reuters.

But things are clearly not looking good. The 2014/15 season, for example, was also the third-driest for South Africa as a whole since the early 1930s, when the country was hit by a historic drought in the midst of the Great Depression.

This season has made a blistering start and the Weather Service said on Tuesday that a heatwave over four provinces covering much of the maize belt was expected to persist until Friday or Saturday.

The financial hub of Johannesburg this week imposed water restrictions on residents which include not filling pools.

And the dry conditions may extend into the autumn because of an El Nino, a warming of ocean surface temperatures in the eastern and central Pacific that occurs every few years and affects weather patterns around the globe.

Dry conditions last year cut South Africa's maize crop by a third and the weather outlook and historic troughs for the rand drove prices for yellow maize, used for animal feed, to 2015 highs over 3,000 rand a tonne on Monday.

South African livestock farmers were urged by the government last week to cut the size of their herds as drought conditions suck moisture out of grazing land.

In the short run this may push down livestock and meat prices but costlier maize - South Africa's staple - will hurt poor households, while rural households will also suffer.

This could have negative political consequences for the ANC in local elections next year. (Editing by James Macharia and Dale Hudson)

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