A weekly update describing soil moisture patterns across the country to show where dry to extremely dry conditions are occurring or imminent. Regions experiencing significant soil moisture deficits are deemed “hotspots”. Persistent hotspot regions have the potential to develop into drought.
Please note that this is the final Hotspot Watch update for this season. The Hotspot Watch will return during spring 2026.
Recent rainfall and current soil moisture conditions:
In the North Island, substantial rainfall amounts were widespread in the past week, with many regions in the southern half of the island receiving 75-150 mm, with isolated amounts of 150-200 mm or more. Much of Waikato and Bay of Plenty received 30-75 mm, with amounts of 30 mm or less observed in Northland and Auckland. This resulted in large soil moisture increases across the central and southern North Island, although slight decreases were observed from Northland to Waikato. The driest soils across the North Island, when compared to normal for this time of the year, are found in southern Gisborne and Māhia Peninsula, while the wettest soils for this time of the year are found in parts of Northland, Auckland, and the east coast from Central Hawke’s Bay to Wairarapa.
The previous hotspot in Wairarapa dissipated in the past week and no hotspots are currently in place across the North Island. As of 20 April, the New Zealand Drought Index (NZDI) map shows that abnormally dry conditions are currently found in coastal Taranaki, and southern Manawatū-Whanganui.
In the South Island, rainfall amounts of 75-150 mm were widespread across the West Coast, Tasman, and North Canterbury in the past week, with isolated higher amounts. Amounts of 30-75 mm were observed in parts of Marlborough, Nelson, interior Canterbury, and Fiordland, with 30 mm or less in central Canterbury, Otago, and much of Southland. At least moderate soil moisture increases were observed nearly everywhere across the South Island in the past week. The driest soils in the South Island, when compared to normal for this time of the year, are located in central Canterbury near Christchurch, while the wettest soils for this time of the year are found in eastern Marlborough and the Kaikōura District.
A very small hotspot remains in place just west of Christchurch. As of 20 April, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in interior Buller District and parts of interior Otago.
Pictured above: Soil Moisture Anomaly Maps, relative to this time of year. The maps show soil moisture anomalies over the past two weeks.
New Zealand Drought Index (NZDI)
As of 20 April, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in coastal Taranaki, southern Manawatū-Whanganui, interior Buller District, and parts of interior Otago.
Please note: some hotspots in the text above may not correspond with the NZDI map. This difference exists because the NZDI uses additional dryness indices, including one which integrates the rainfall deficit over the past 60 days. Changes are therefore slower to appear in the NZDI compared to soil moisture anomaly maps that are instantaneously updated.
The week ahead:
In the North Island, a very localised area of moderate to heavy rain will likely affect southern Northland and northern Auckland on Friday and early Saturday (24-25 April). Otherwise, a large area of high pressure will sit over the North Island during the next week or more, resulting in almost completely dry weather. Weekly rainfall totals could reach 50-100 mm in a localised part of southern Northland and northern Auckland. However, the remainder of the North Island will see only very meagre rainfall totals of less than 5-10 mm, with some areas receiving no rainfall at all.
Due to the expected rainfall in the next week, a majority of the North Island will see small to moderate soil moisture decreases with the exception of the small region expected to see moderate to heavy rain in the next day or two. No hotspots are expected to form in the next week across the North Island.
In the South Island, a broad area of high pressure will result in generally dry weather over the next week or more, although occasional passing fronts will affect areas such as Fiordland, Southland, and Stewart Island at times. Weekly rainfall totals of 30-60 mm will be possible in Fiordland, Southland, and Stewart Island, with much lighter amounts in Otago and the West Coast. Meanwhile, the remainder of the South Island will see little if any rainfall over the next week.
Due to the expected rainfall in the next week, soil moisture levels will likely decrease nearly everywhere in the South Island except across Southland and Fiordland. The current hotspot near Christchurch will likely strengthen somewhat in the next week, with a slight chance that a new hotspot will form in interior Otago.
Long-term outlook (through late May):
- The drier (25th percentile) and middle (50th percentile) scenarios both show significant dryness across large swathes of both islands.
- Even the wetter (75th percentile) scenario shows drier than normal conditions in the western North Island and parts of the South Island.
- Notably, wetter than normal conditions are indicated for the eastern North Island in all three scenarios.
Pictured above: 35-day forecast rainfall anomaly scenarios (Top), and 35-day forecast dryness and drought scenarios (Bottom). These maps are updated daily at https://niwa.co.nz/climate/seasonal-climate-outlook
Background:
Hotspot Watch: a weekly advisory service for New Zealand media. It provides soil moisture and precipitation measurements around the country to help assess whether extremely dry conditions are imminent.
Soil moisture deficit: the amount of water needed to bring the soil moisture content back to field capacity, which is the maximum amount of water the soil can hold.
Soil moisture anomaly: the difference between the historical normal soil moisture deficit (or surplus) for a given time of year and actual soil moisture deficits.
Definitions: “Extremely” and “severely” dry soils are based on a combination of the current soil moisture status and the difference from normal soil moisture (see soil moisture maps at https://www.niwa.co.nz/climate/nz-drought-monitor/droughtindicatormaps)
Hotspot: A hotspot is declared if soils are "severely drier than normal" which occurs when Soil Moisture Deficit (SMD) is less than -110 mm AND the Soil Moisture Anomaly is less than -20 mm.
