A brief summary of climate and hydrological conditions in the region.
This service is regularly 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. Outside of dry periods, less frequent updates synchronise with our latest seasonal outlooks.
Updated 23 December 2024
Next update due when there is a significant change of conditions or a new seasonal outlook.
Background
The El Niño/Southern Oscillation (ENSO) event responsible for the drought last summer is now swinging back to a La Niña signature. After a moderate hydrological winter recovery, the period from November through to mid-December was exceptionally dry in the Wairarapa. This extreme dryness was then followed by a significant recovery just before Christmas, as the synoptic circulation changed to strong easterly flow. This dramatic reversal was an atmospheric response to both La Niña and local marine heatwaves, with enhanced evaporation in the warm oceans around New Zealand.
Current situation
Soil moisture levels are now below average for most of the eastern hill country, and the national drought index is showing the eastern Wairarapa to be classed as dry, but with a moderate recovery around Christmas. The combined dry and warm conditions have seen river and stream levels steadily fall with low flow restrictions being triggered in some of the valley floor streams and smaller foothill rivers in early December. Restrictions have been on the cusp of becoming more widespread in the Wairarapa before the switch to wetter conditions occurred at the end of the year.
Whether the change in atmospheric circulation persists into the new year and provides rivers and streams with an opportunity for base flow recovery will need to be monitored. Groundwater levels in the Hutt and Kāpiti aquifer systems were at relatively normal levels at the end of the year. However, in the Wairarapa (Ruamāhanga catchment) groundwater levels have been lower than usual with some sites sitting below the 10th percentile (that is, 90% of historical water level measurements for that site at the same time of year have been higher).
Meteorological outlook
International climate models are predicting that the atmosphere will likely remain below the official La Niña threshold. However, as the climate change signal in the oceans around New Zealand tends to naturally amplify local marine heatwaves, and these were already well established by Christmas, we should expect a summer with intermittent La Niña impacts. This implies a further development of moist north-easterly flow episodes in between drier periods of westerlies. There is high likelihood of thunderstorms and recovery periods similarly to the weather event before Christmas in the Wairarapa. Careful monitoring is recommended as the weather patterns should remain highly irregular, but the likelihood of very severe or prolonged droughts over summer has been reduced for now.
Climate change
The ‘normal’ longer-term water balance is becoming increasingly hard to maintain quite possibly due to climate change influences, 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 were to successfully contain global warming under 1.5-2 degrees (the Paris Agreement’s ambition), it is important that we enhance our water resilience and be prepared for more unreliable climate patterns with both extreme dry and extreme wet periods. We note that the warming of the land also means that evapotranspiration will greatly increase, so the soil will likely need more ongoing rain to maintain ideal moisture levels, compared to what it has needed in the past.
View the latest national drought index state
View the national drought forecasting dashboard
View the latest seasonal report:
Climate drivers and seasonal outlook for the Wellington Region - Spring 2024 summary Summer 2024-2025 outlook
Spring 2024 was the warmest on record for Wellington and Paraparaumu, with data available since 1928 for Wellington and since 1953 for the Kāpiti Coast. Various warm nighttime records were… Read more here
date_range Published 18 Dec 2024
Download now (PDF 1.8 MB) get_appBrowse the data
Anomaly Maps
How different has recent rainfall/soil moisture been compared with the same time in previous years?
Site-specific graphs
| Area | Rainfall | Soil Moisture |
| 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 |
Get in touch
- Phone:
- 0800496734
- Email:
- info@gw.govt.nz