A cluster of lightning strikes struck Invercargill yesterday, blowing phone jacks out of walls, damaging electrical equipment and cutting electricity in part of the city.

Wet and wild weather that began in the early hours of yesterday morning culminated in a series of lightning strikes in north Invercargill about 9am.

Several houses in Talbot St were struck by bolts, described by one resident as a "fireball".

Daniel and Anne Phillips were at their house when the lightning struck, blowing phone jacks out of the wall and shattering light fixtures.

Mr Phillips described the strike as a flash and a huge bang but his wife had a different experience.

"I saw from the kitchen window a fireball ... it went like a flash, it was a little slower that but the explosion seemed to hit the house," she said.

Telephones and the Sky TV decoder had been fried and power had been lost for several hours but at least they were warm again, Mr Phillips said. "The heatpump's going and that's the main thing."

Their neighbours Diana and Tom Watt were not so lucky, being without a heatpump until after 1pm. Mr Watt described seeing sparks shooting down the road from power lines and their neighbour's garage had a chunk blown off the outside.

Nearby Salford School was also struck as pupils were arriving at school. Principal Marlene Campbell said phones and fire alarms had been knocked out and sparking wires had flown past her office window.

PowerNet and James Hargest College had fire alarms set off during the strikes and the Tiwai Point aluminium smelter had minor disruptions to its phone system.

The Milford road was reopened at 11am yesterday after being closed overnight.

NZ Transport Agency operations manager Murray Clarke said it was a precautionary measure after last week's earthquake in case of rockslides. The road was closed again yesterday evening because of another heavy rain warning, Mr Clarke said.

MetService forecaster Heath Gullery said a deep low passing near the South Island had caused unsettled westerlies across the region. Winds gusting up to 95kmh were recorded at Invercargill Airport but only 13mm of rain fell overnight because of the speed of the storm, Mr Gullery said.

Another southwest change was expected this afternoon, with squally showers and the possibility of more thunderstorms and hail with snow down to 200m, he said.