Law said Wellington was likely to be one of the North Island's bright spots, staying dry tomorrow, but with cloud on Sunday.
Runners taking part in the ASB Auckland marathon events on Sunday can, on MetService's current forecast, expect a partly cloudy day with a few afternoon showers, northeasterly breezes and a high of 21C.
"Hopefully it will stay dry for the race itself," Law said.
MetService forecast
Auckland
Tomorrow
Mostly cloudy with occasional rain, easing evening. Light winds. 19C
Sunday
Partly cloudy, a few afternoon showers. Northeasterly breezes. 21C
Hamilton
Tomorrow
Mostly cloudy with a few showers. Light winds. 18C
Sunday
Cloudy periods, occasional showers. Northeast breezes. 20C
Tauranga
Tomorrow
Mostly cloudy. Showers turn to rain late morning. Light winds. 18C
Sunday
Often cloudy, showers ease evening. Northeast breezes. 18C
Wellington
Tomorrow
Fine with occasional high cloud. Light winds. 19C
Sunday
Cloud increasing, chance afternoon shower. Northerlies developing. 18C
Christchurch
Tomorrow
Mainly fine, some morning cloud. Northeasterly breezes. 18C
Sunday
Fine with northeast breezes. 22C
Dunedin
Tomorrow
Morning and evening cloud, otherwise fine. Light winds. 16 C
Sunday
Mostly sunny but some morning cloud. Northeast breezes. 21C