This webpage provides a brief summary of climate and hydrological conditions in the region. This service is only updated during periods in which closer monitoring is required (regardless of time of the year), in recognition that there is potential for dry spells, or irregular hydrological recharging. It does not define an official council position on drought or drought declaration.
The difficult ‘Coronavirus year’ of 2020 was characterised by an extremely dry and variable rainfall pattern in our region, failing to achieve full hydrological recovery by winter.
This was followed by the wettest spring on record in Wellington, and the third wettest spring on record in Masterton. The La Niña summer of 2021 followed with a mostly dry pattern as predicted, with the total seasonal rainfall mainly between 60 and 80% of the average for most of the region.
As a result of the ups and downs, the current hydrological year (1 June 2020 to 31 May 2021) is so far looking near normal for most areas, and deficient in the high elevations of the Tararua ranges. The national drought index from NIWA indicates that most of the region is either dry or extremely dry.
This is a slight improvement in relation to more severe conditions observed at the same time last year for most of the North Island. In any case, climate change research suggests that a dry background state will likely become the ‘new norm’, as the temperatures continue to increase.
The La Niña event is now slowly starting to dissipate, even though its influence is still expected to be felt over New Zealand during most of autumn. This has been a very unusual La Niña, with the weather patterns erratically alternating between westerlies and easterlies. The Sea Surface Temperatures (SST) around New Zealand have also been very variable, mostly responding to variations in the atmospheric circulation itself, rather than driving a stable seasonal climate regime.
With La Niña slowly dissipating and most climate drivers being near-normal, the expectation is that autumn will oscillate between longer settled and warm periods, and colder south-westerly flow. A more “normal” rainfall pattern is expected, with higher probability of extreme rainfall events during the season.
In light of a warm background SST and air temperatures, the current dryness still has potential to increase towards the end of the warm season, even though the climate drivers’ behaviour in general is not conducive to a main drought.
The ‘normal’ longer-term water balance is becoming increasingly hard to maintain due to climate change and increased high frequency climate variability, with more unreliable weather patterns.
Droughts are expected to become more severe and frequent in the Wellington region, particularly in the Wairarapa. Even if international climate policy efforts successfully contain global warming under 1.5-2 degrees (the Paris Agreement’s ambition), it is important that we build water resilience and be prepared for a “new normal” climate pattern, significantly drier than in the past.
We note that the warming temperatures also mean that evapotranspiration is greatly increased. There is some evidence that our soils are getting drier, and ground water storage may be decreasing, in the long-term.
How different has recent rainfall/soil moisture been compared with the same time in previous years?
Click on the links below to see the relevant anomaly map
|Kapiti Coast (lowland)||Otaki at Depot|
|Kapiti Coast (high altitude)||Penn Creek at McIntosh|
|Porirua||Horokiri Stream at Battle Hill
|Wellington City||Kaiwharawhara Stream at Karori Reservoir|
|Hutt Valley (upper catchment)||Hutt River at Kaitoke Headworks|
|Upper Hutt||Upper Hutt at Savage Park||Upper Hutt at Savage Park AQ|
|Wainuiomata||Wanuiomata River at Wainui Reservoir|
|Wairarapa (high altitude)||Waingawa River at Angle Knob|
|Wairarapa Valley (north)||Kopuaranga River at Mauriceville|
|Wairarapa Valley (Masterton)||Ruamahanga River at Wairarapa College||Wairarapa College AQ|
|Wairarapa Valley (south)||Tauherenikau River at Racecourse||Tauherenikau River at Racecourse|
|Wairarapa (north-eastern hills)||Whareama River at Tanawa Hut||Whareama River at Tanawa Hut|
|Wairarapa (south-eastern hills)||Waikoukou at Longbush||Waikoukou at Longbush|