Auckland is almost at a standstill as it braces for the worst from Cyclone Gabrielle.

Commuter trains in the city have been cancelled until at least 3pm, the harbour bridge has reopened but with lane and speed restrictions, and most schools in the region have shut their doors.

Delays are also expected for bus services depending on the impact of the cyclone and ferry services are likely to be cancelled as conditions worsen.

Air travel is also impacted as Air New Zealand has cancelled all domestic flights from or through Auckland, Hamilton, Tauranga and Taupō, until at least midday on Tuesday.

And non-essential services in Auckland, including libraries, community centres, early childhood education centres, and active recreation centres are all shut.

Meanwhile, power outages have been widespread overnight and thousands are without power across Northland, Auckland and the Coromandel Peninsula.

Twenty-six emergency shelters and civil defence centres are now open across Auckland.

MetService and Niwa are warning the worst is likely yet to come as Cyclone Gabrielle moves down the country, with significant wind and rain expected across Northland, Auckland, Coromandel, the East Coast including Tairāwhiti, and Hawke's Bay.

What you need to know:

• Northland, Auckland and Coromandel are in a state of emergency due to the threat posed by Cyclone Gabrielle.
• Thousands of people are without power across Northland, Auckland and the Coromandel Peninsula.
• Commuter trains in Auckland have been cancelled until at least 3pm.
• Air New Zealand has cancelled all domestic flights from or through Auckland, Hamilton, Tauranga and Taupo, until at least midday Tuesday.
• Some international flights are also either cancelled, or diverted to another NZ airport.
• Most schools in the region have closed and all non-essential services in the city, including libraries, community centres, early childhood education centres, and active recreation centres are all shut.
• The cyclone has been downgraded to a sub-tropical low pressure system from a Category 2 cyclone.
• Heavy rain in the north and east is expected to spread southwards to the rest of the upper and central North Island this afternoon.
• East to southeasterlies gales will be severe in many places, turning southwesterly over Northland this afternoon.
• Impacts of Gabrielle are expected to spread through to northern parts of the South Island today and Tuesday.
• MetService and Niwa are warning the worst is likely yet to come as Cyclone Gabrielle moves down the country.
• Twenty-six emergency shelters and civil defence centres are now open across Auckland.

UPDATED FEB 13, 2023 6:40 AM