MetService meteorologist Tom Adams said there had been 1700 lightning strikes on the West Coast in two hours, many of which struck around the Nelson area.
"It was definitely visible from the city," he said. "In terms of the severity, it is a bit early to know because it has only just gone through to know if there are any reports of localised flooding but ... there were definitely some short sharp rainfall numbers."
Mr Adams said the bad weather was due to hit Wellington in the next few hours. He said it was not, however, expected to be as bad in the capital because it was somewhat sheltered from the west.
Some isolated gusts of about 60km/h were recorded in Hawke's Bay yesterday and more were forecast, but fine weather is forecast for Hawke's Bay on Thursday.
A low rotating over the South Island on Friday would "hopefully" bring some rain to Hawke's Bay, a forecaster said.
"This is classic autumn," he said. "This sort of flip-flopping can be expected throughout the week and the weekend."