Cyclone Tam is expected to remain slow-moving over the Tasman Sea today. It directs a moist northeast flow over the country with several unstable fronts and troughs moving onto the country. There is a general low risk of thunderstorms for the northern part of the North Island, from Taranaki to northern Gisborne/Tairawhiti and about the Tasman District and northern Buller during the day. At night this low risk area spreads southeast to cover Taumarunui, Taihape, the Hawke's Bay ranges and southern Gisborne/Tairawhiti. This afternoon and evening, the risk of thunderstorms increases to moderate for northern Northland and Bay of Plenty from Rotorua eastwards. These thunderstorms may be accompanied by localised heavy rain with intensities of 10 to 25 mm per hour, and for Bay of Plenty there is a low risk of downpours with intensities of 25 to 40 mm per hour. For southern Northland, the risk of thunderstorms is moderate this evening and tonight, possibly bringing localised heavy rain with intensities of 25 to 40 mm per hour. Tonight there is also a low risk of downpours of 25 to 40 mm per hour. Tonight, the risk of thunderstorms about western Tasman District also increases to moderate and there is a chance of localised heavy rain with intensities of 10 to 25 mm per hour. No other areas of severe convection or thunderstorms are expected.

Cyclone Tam, over the Tasman Sea, moves very slowly towards the northern South Island during the day. Fronts and troughs associated with the cyclone continue to cross the country. There is a generally low risk of thunderstorms for the north and west of the North Island and for the northwest of the South Island. For southern Northland, Auckland, Waikato and Coromandel Peninsula, the risk of thunderstorms is moderate during the morning. These thunderstorms may bring localised heavy rain with intensities of 10 to 25 mm per hour and a low risk of downpours of 25 to 40 mm per hour. There is also a moderate risk of thunderstorms during the morning for Taranaki, Tasman District and Nelson, and for the pre-dawn period for eastern Bay of Plenty. These thunderstorms may bring localised heavy rain with intensities of 10 to 25 mm per hour. No other areas of severe convection or thunderstorms are expected.

Cyclone Tam continues to approach the northern South Island. Some, generally weaker, troughs cross the country. There is a low risk of thunderstorms about the west and north of the North Island and the northwest of the South Island. During the afternoon, there is also a low risk of thunderstorms about the inland areas of Whanganui, Manawatu, Hawke's Bay, Wairarapa and Kapiti. During the afternoon, there is a moderate risk of thunderstorms about southern Coromandel Peninsula, far western Bay of Plenty, coastal Waitomo, Taranaki, Tasman District, Nelson and parts of western Marlborough. These thunderstorms may bring localised heavy rain with intensities of 10 to 25 mm per hour. No other areas of severe convection or thunderstorms are expected.