A big low developing in the Tasman Sea this week will roar into life out at sea over the next 24 hours before falling apart as it moves into New Zealand mid to late in the week. The low will peak in intensity tomorrow, Tuesday, but will be out at sea. It weakens as it moves into New Zealand but will still bring a couple of days of wind, rain and showers.
This low will encourage more of the hot, humid, airflow from the sub-tropics continuing the heatwave in the lower South Island with highs as much as 35 degrees C possible today and tomorrow, especially around Central Otago.
By Wednesday the rain clouds arrive on the West Coast and by Thursday heavy downpours will cross the North Island also.
A cooler change moves into the lower South Island later this week, but the sub-tropical airflow looks likely to remain in the north into the weekend.