People in Auckland and Northland are being advised to tie down loose objects as a storm packing gale-force winds of up to 120km/h is expected to lash the region tonight.
MetService meteorologist Tui McInnes said the storm could be strong enough to blow objects into the air.
"You might see your trampoline has tipped itself over," he said.
"Don't keep loose things around in your garden that could be picked up by the wind and rolled into a glass window."
The bad weather forced play to be suspended at the McKayson New Zealand Women's Open golf tournament in Auckland this morning.
The host course Windross Farm was subjected to steady rain this morning, with surface water amassing on the greens. Play resumed at lunchtime.
Meanwhile the high winds, which hit Auckland only three times a year on average, are expected to hit the region from Coromandel northwards this evening and into the early hours of tomorrow morning, with a lower possibility of high winds in Hawke's Bay.
"The gales are expected to become severe, gusting 120km/h in exposed parts of Northland and Auckland north of the Harbour Bridge during this period," a MetService advisory warned.
The NZTA warned drivers to take "extreme caution" on the Harbour Bridge this evening.
McInnes said by 6am tomorrow most of the strong winds should be easing.
He said the rain which has hit much of the North Island this morning is the "precursor" to the bad weather on its way across the Tasman Sea.
"It's wet for most. It's pretty persistent now but the showers in behind mean it's probably not going to feel like it's getting any clearer," he said.
However the storm is not bringing cold weather, with typical spring daytime highs expected in Auckland of 15C today and 17C from Monday through to Friday.
The South Island is "the nicer island at the moment" with a mostly cloudy day outside the West Coast.
Some sunny spells are expected in the north after the storm passes tomorrow before another, milder cold front brings more rain by the end of the week.
Electricity lines company Vector reiterated the MetService warning about tying down loose things outdoors.
"As always, we'll have crews on standby in case wind or trees bring down power lines, although our crews may be unable to attend while the wind poses a safety risk.
"If you do happen to see lines down, always treat them as live. Keep well away and call 0508 VECTOR (0508 832 867) to let us know."