Powerco has asked customers in the Whanganui, Taranaki, South Waikato and Coromandel areas to brace themselves for high winds and heavy rain from Tuesday afternoon.
Powerco Network Operations Manager Phil Marsh said an approaching storm was due to affect those areas from 3pm Tuesday until 3am Wednesday.
"Winds up to 120km are expected so any loose objects are certain to become airborne," he said.
Trampolines, outdoor furniture and other heavy items should be securely fixed to the ground.
"Falling branches and toppling trees are other hazards in weather events like these so downed lines must be treated as live at all times. Stay well clear and call Powerco on 0800 272727 for emergencies such as trees in power lines or lines down," he said.
Temperatures are forecast to plummet as the cold, southerly blast sweeps through.
"There is a chance of snow in the Central Plateau region so customers there should be ready to cope with that as well," he said.
Powerco is New Zealand's second largest electricity utility and largest gas distribution utility with around 442,000 consumers connected to its networks.
Powerco's electricity networks are in Western Bay of Plenty, Thames, Coromandel, Eastern and Southern Waikato, Taranaki, Whanganui, Rangitikei, Manawatu and the Wairarapa.
Its gas pipeline networks are in Taranaki, Hutt Valley, Porirua, Wellington, Horowhenua, Manawatu and Hawke's Bay.
Read your forecast here: Whanganui weather