The heaviest downpours were falling between Kaitaia and Whangarei, especially around the Bay of Islands. The rain would be heavy enough to cause localised surface flooding and hail, forecasters said.
WeatherWatch said the Auckland region was mostly dry but a couple of big, isolated showers were affecting a few areas to the northeast and southeast of the city.
However, most activity was inland, outside the city.
MetService meteorologist said Auckland's ground temperature was a relatively mild 14C, but the clouds hanging over the region were packing some hail.
"It's a case of 'do they get to the ground before they melt?"'
Ms Murray said the day would bring "sleety showers" and there was a moderate risk of thunder storms from a trough moving over Auckland.
"We haven't seen any lightning strikes over Auckland. We had one in Waikato but that's about it. We're still monitoring. As the heat of the day increases we might get one or two more."
This afternoon, the bad weather was continuing to move east to west, with big showers possible in Coromandel, Thames, Waikato and the inner North Island as far south as Manawatu and Hawkes Bay. Localised surface flooding and hail were both possible.
WeatherWatch said there would be plenty of long dry spells in the mix too.
"It's a day that's mainly dry but with a high risk of a downpour. As we go through this afternoon that is exactly what we are seeing.
"Showers will continue to build this afternoon under warm conditions -- and many showers will drift east, but a few may simply grow where they first formed, then fade out in the same spot towards evening."
Most showers would ease this evening, but a few isolated showers may pop up again tomorrow afternoon in the upper North Island.
Elsewhere in New Zealand was mainly dry today.
