Much of the country is bracing for more violent electrical storms today as Roxburgh remains cut off and cleaning up from Sunday's storm.
MetService says the risk of thunderstorms this afternoon and evening is high for inland parts of the North Island from Waikato south.
Auckland, Coromandel Peninsula, inland Gisborne and parts of Northland have also been put on notice but the risk of storms is lower.
Today's thunderstorms are expected to bring heavy localised deluges with large hail stones. Some storms are expected to be so intense, up to 40mm of rain could fall in an hour sparking flash floods and slips and driving could be hazardous.
Virtually all inland South Island regions are being told to brace for thunderstorms for the fourth day running.
Localised storms are expected to strike from the Nelson Ranges to Central Otago and the Southern Lakes after lunch until tonight.
MetService said unstable conditions over inland central and lower North Island and inland areas of the South Island meant heavy showers and isolated thunderstorms were likely in many places.
Yesterday more than 10,000 lightning strikes were recorded over the country and severe thunderstorm cells sparked warnings for the Mackenzie Basin and Marlborough.
Meanwhile the mop-up is continuing in Roxburgh where SH8 is closed as road crews are clearing slips and repairing washouts on the main highway between Roxburgh dam and Millers Flat.
Lake Roxburgh Village was put under a boil water notice yesterday and residents asked to conserve water.
The Central Otago District Council said building inspectors had now gone through all the buildings affected by the weekend flooding.
It said Roxburgh's water supply sewerage system and road access was not yet restored.
Roxburgh Area School remained closed today after floodwaters coursed through several classrooms leaving a large amount of silt in the school grounds. Part of the back field and fence disappeared in the deluge.
Principal Gary Pasco said much of the silt had been cleared but the school could not open until water and sewage facilities were fixed, probably today.
The school's end-of-year prizegiving, which was scheduled for tonight, was being put off until next week given the community was still having to cope without water and toilets.
This morning the council asked Roxburgh residents not to use river water to flush home toilets as the sewage system was not able to cope.