Power outages are being reported in the Western Bay of Plenty and Coromandel as heavy rain and strong winds lash the region.

A severe weather warning for heavy rain was issued overnight and remains in place today.

Powerco is reporting power cuts to 208 properties in Aongatete, 35 properties in Karangahake and 478 properties in Hikuai in the Thames/Coromandel area.

The power company says these are unplanned outages and site investigations are underway.

Meanwhile, a thunderstorm watch issued by the MetService earlier this morning has now been upgraded.

The weather organisation says a severe thunderstorm watch for Auckland has been lifted, but now extends southwards to include most of Waikato.

'A frontal system and associated heavy rain is moving south over Coromandel Peninsula and Waikato.

'There is a high risk of thunderstorms embedded in the rain. These thunderstorms are expected to bring heavy rain with intensities of 15 to 25mm/h, and strong winds gusting 90 to 110km/h.

'Additionally, some of these thunderstorms could become severe, producing localised downpours of 25 to 40mm/h, as well as localised torrential rain with intensities greater than 40mm/h.

'There is also a risk of damaging winds and a localised tornado occurring.”