Otago is heading for a scorching summer as El Nino tightens its grip on the country.
MetService meteorologist Georgina Griffiths said this year's El Nino would go close to equalling the strength of the 1997-98 one in the region and would depend a lot on how Australia's summer panned out.
In 1998 Australia experienced warm afternoons and was hot and dry. That ''nasty'' heat ended up ''baking'' Otago, she said.
''Dunedin has experienced a rather cool few months. This is standard El Nino fare - cool winters, then colder than usual springs.
''If ... Aussie gets very dry [and] hot, then any northwesterlies after Christmas may well yield some extreme hot temperatures for Dunedin.''
There would be big swings in temperatures until Christmas. After that, things would really start to heat up, Ms Griffiths said.
Otago has already experienced huge swings.
Temperatures in the high 20s and gale-force winds last month sparked damaging vegetation fires in Dunedin, Dunback and Oamaru, while on Monday snow was forecast to 400m for the region in an event described by MetService as unseasonable.
National Institute of Water and Atmospheric Research National Climate Centre principal scientist Chris Brandolino said El Nino would affect Otago either by a drier summer than usual or more rainfall.
The effect would be determined by wind direction. Southwesterly winds indicated more rainfall in the area while predominantly westerly winds, which came off land, increased the chance of a significant dry period.
''It well and truly depends on how the wind sets up. That will have a lot to say,'' he said.
There was an elevated risk of drought later in the summer, particularly in the east of the South Island, and the three El Ninos since 1950 all produced ''very dry conditions'', Mr Brandolino said.
An El Nino in 1997-98 produced a severe dry spell in Otago, especially in the east of the region.
Niwa released its November to January outlook on Monday, stating a rise in sea surface temperatures in parts of the Pacific by 2.5degC-6degC, indicated El Nino was sure to continue over the next three months.
Above-normal air pressure to the north and west of New Zealand and below-normal air pressure in the south, accompanied by ''anomalous'' west-southwesterly winds, also signalled signalled El Nino weather conditions.
