This is the full reference version: every region's typical last spring frost and first autumn frost, in one place, sourced from Earth Sciences New Zealand's official ground-frost climate normals rather than estimated. Treat it as a map to check against, not a forecast for any single year.
Frost-free or close to it: Northland sees so little ground frost in an average year that a "last frost date" isn't a particularly useful planting guide there at all.
Clearing earliest, by August or September: Wellington (August) and Auckland (September) both lose their frost risk well ahead of most of the country, Wellington despite its southern latitude, largely because of its coastal exposure and near-constant wind.
Clearing earliest, by August or September: Wellington (August) and Auckland (September) both lose their frost risk well ahead of most of the country, Wellington despite its southern latitude, largely because of its coastal exposure and near-constant wind.
Clearing by October: Hawke's Bay and Taranaki, with the first autumn frost not returning until May in both, and the West Coast, which clears around the same time despite its very different, much wetter climate.
Clearing by November, autumn frost returning March to May: Waikato, Bay of Plenty, Gisborne, Manawatū-Whanganui, Nelson, Tasman, Marlborough and Otago. This is the largest single group, and it's the band the traditional Labour Weekend planting rule was really built around, even though it doesn't fit the country's earlier regions or its one true outlier. Otago's inclusion here surprises people: the region's winters are genuinely harder than Waikato's, but the two share the same last-frost month regardless.
Clearing latest of any region with a genuine frost-free season: Canterbury, commonly not until December.
No real frost-free window at all: Southland's own climate data shows measurable ground frost recorded in almost every month of the year on average. A fixed last-frost date isn't a meaningful planting guide there the way it is everywhere else on this list, and a greenhouse, cloche or cold frame does more for a Southland garden's tender crops than timing ever will.
For a specific region's exact month range alongside what to actually plant once frost risk has passed, this site's regional spring planting guides go further than this reference list does on its own, and this site's planting calendar breaks the same timing down crop by crop.