A thunderstorm watch is in force for the Coromandel this afternoon.
As well as Coromandel, the MetService has issued the watch for Northland, Auckland, Great Barrier Island and the Waikato.
"A very moist northwest airstream extends onto the North Island, bringing a moderate risk of thunderstorms to northern regions today," says a statement from the weather organisation.
"Additionally, there is now a moderate risk that some of these thunderstorms may become severe, with localised downpours of 25 to 40 mm/h possible in Northland, Auckland, Coromandel Peninsula and the far northern parts of Waikato this afternoon and evening.
"Rainfall of this intensity can cause surface and/or flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips.
"Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain."