Forecasting principal scientist Chris Brandolino said a weak, central Pacific El Nino continued during June as sea surface temperatures remained more than 0.7degC above average for the fourth consecutive month.
While El Nino was expected to continue over the coming three-month period, it might gradually weaken and become less influential on the global climate system, he said.
For the July to September period, air pressure was forecast to be higher than normal to the northwest of New Zealand and lower than normal to the south.
''This is expected to be associated with more westerly-quarter winds to start the season and mixed flow patterns later.
''There may be a trend towards more unsettled weather during the coming season, particularly in September.''
As a result, temperatures were forecast to be near average or above average for Otago and Southland, but the weather might become more ''unsettled'' in the latter months, particularly in September.
''Warm spells are possible on occasions during July and particularly August when air flows extend from Australia from time to time.
''Despite a low chance for below-average seasonal temperatures, cold snaps and frosts remain likely to occur.''
As the season progressed, high-pressure systems might become less frequent across the country, contributing to more regular rainfall events, he said.
In inland Otago and Southland, rainfall, soil moisture levels and river flows were likely to be in the near normal range.
In coastal Otago, rainfall totals were likely to be near normal or below normal, and soil moisture levels and river flows were likely to be near normal, he said.
