A strong cold change's set to creep up the South Island today, and replace the hot weather

It'll bring heavy showers, thunderstorms and a dramatic turn in the temperature heading into tomorrow.

However, before it arrives, temps across the top of the South Island could climb as high as 29 degrees in Blenheim.

MetService meteorologist John Law says in the north, Northland and Bay of Plenty can expect showers this afternoon.

He says the southerly change running up Otago and Canterbury is set to bring a dramatic shift in the weather ... stronger winds, thunderstorms, hail and a real drop in the temperature.