"It won't feel like summer for some southern and western coastal areas. Parts of Southland and Otago will only just break into the low teens by middle of next week," Duncan said.
"Auckland has a high of only 19 next Wednesday, well down on recent weeks."
The normally hotter areas, like the Bay of Islands and Hawke's Bay will get highs only in the late teens or early 20s - about 10C lower than their recent highs.
There will be more clouds, which not only contribute to the drop in temperatures but also make it seem like rain is coming. However, the possibility is only for brief showers.
Expect wet and windy conditions for parts of southern and central New Zealand as an active front from the Southern Ocean moves across the country on Sunday.
MetService is predicting strong to gale southwesterlies for the South Island that could bring a chance of summer snow to 1200m by Monday.
The strong southwest flow is forecasted to continue well into next week.
The deep south is expected to get the worst of the weather, with highs of just 13C for Saturday and 14C for Monday and Tuesday.
Auckland is expected to reach just 20C tomorrow and remain in the low 20s through the week, and there are more showers to come.
Southerlies will keep Wellington struggling to reach 20C for most of next week, and temperatures in Christchurch will only be around 20C from Tuesday to Thursday.
True summer temperatures will return only late next week, as high pressure brings sunnier skies and warmer weather as it expands across the country.
"By next weekend we may be back to sub-tropical northerly quarter winds," Duncan said.
"But this may also bring a surge of windier weather back, perhaps to Cook Strait, Wellington and other surrounding areas."
