Heavy rain is forecast to continue over the Auckland region today, while fog has delayed flights in Christchurch this morning.
MetService has a severe weather warning in effect for Auckland, with "periods of heavy, thundery rain" expected until early this afternoon.
Up to 50-60mm of rain is possible in some parts of Auckland, with peak intensities in excess of 20mm per hour.
A severe thunderstorm watch is also in force for Auckland, the Great Barrier Island and Coromandel Peninsula, with the possibility of heavy thundery rain over those areas between 9am and 2pm.
The thunderstorms are forecast to move over Auckland over the next three hours.
MetService warns the heavy rain may cause flash flooding and slips, and advises motorists take care on the roads.
Meanwhile domestic flights in and out of Christchurch Airport are delayed this morning due to heavy fog.
An incoming flight from Auckland has been diverted back to the city.
People should check with their airlines about potential delays.
Alpine roads on the South Island are forecast to receive snowfalls later today and tomorrow, with Milford Road, Lindis Pass, Porters Pass and Lewis Pass all expected to have snow accumulate near their summits.