August 2026 climate report

August has seen winter begin to fade and spring-like conditions starting. There has been lots of temperature variability and dominant westerly flows. The month began drier than average, however towards the end of the month a burst of subtropical airmass raised rainfall totals especially in the Far North, Hokianga and Eastern Coastal areas from Bay of Islands to Whangārei Heads. Kaikohe, Opouteke, South of Whangārei close to the regional border, across the Kaipara from Kai Iwi Lakes extending to Pouto Point had below average rainfall. River flows are generally low for August due to average rainfall. Soil moisture received respite, groundwater has received more recharge.   

Summary

• Northland’s average rainfall was 172 mm, which was 108% of expected rainfall for August. 
• August river flows for Northland range from “Normal” to “Extremely Low” across the region. Primarily “Below Normal” to “Very Low”. River flows are generally lower through western, mid-north and southern parts of the region, there has been some recovery of Eastern Coastal levels reflecting August’s rainfall distribution.  
• Higher rainfall totals this month have contributed to groundwater recharge. Most levels are “normal” or “below normal” for most of the region for this time of year.  
• Regional soil moisture is about normal for this time of year with most sites at field capacity. 
• El Niño conditions persist and have strengthened considerably during this month; especially since mid-winter. Impacts on Northland’s weather patterns are starting to be felt and will persist through the year. The El Niño event is comparable to 1997 and has shown the strongest warming trend on record.  
• El Niño typically brings drier weather to Northland.  

Rainfall

• Northland’s average rainfall was 172 mm across the region for August (Figure 1), which is 108% of the long-term median, or normal expected rainfall (Figure 2) for the month. Most of this rain was focused in the Far North, Hokianga and Eastern Coastal areas from Bay of Islands to Whangārei Heads. 
• The highest rainfall total for the month was recorded at Touwai at Weta with 325.5 mm, 147% of normal expected. 
• Other high recording rainfall stations include: Whakapara at Puhipuhi with 305mm, 151%; Purerua Peninsula BOI with 296.1 mm, 207%; Punaruku at Ōtetao Reti Marae with 293mm, 169%; Veronica Channel at Opua Wharf with 258mm, 174% Kerikeri at BOI Golf Club 256.5 mm 142%; Cape Reinga with 186.9mm, 181%; Whangārei Harbour at Marsden Point with 178mm, 148% of normal expected rainfall for the month. 
• The lowest rainfall for August was recorded at Dargaville with 60.2 mm, which is 48% of normal expected rainfall. 

Figure 1 and 2: August 2026 rainfall distribution for Northland in mm, and in percentage of median. Showing an average of 172mm (108% of expected) rainfall for the region.

Figure 3: Winter 2026 rainfall distribution for Northland in percentage of median. Showing a maximum percentage of 124% rainfall for the region.

Winter seasonal rainfall was 82% of expected median with 124% being the maximum received at Takahue at Saddle Road (Figure 3).  

Figure 4 and 5: Standardised rainfall for Northland on a 3-month period June to August 2026 and a 6-month period March to August 2026.

River flows

August river flows for Northland range from “Normal” to “Extremely Low” across the region. Primarily “Below Normal” to “Very Low”. River flows are generally lower through western, mid-north and southern parts of the region, there has been some recovery of Eastern Coastal levels reflecting August’s rainfall distribution.  

Figure 6: River flows in Northland for August 2026

Groundwater

Higher rainfall totals this month have contributed to groundwater recharge. Most levels are “Normal” or “Below Normal” for most of the region for this time of year. The exceptions are Aupouri and Mangawhai where levels are “Above Normal”; Taipa, Poroti, Maungatapere and Maunu are “Low”; Taipa and Awaroa where levels are “Extremely Low”. 

Figure 7: Groundwater levels in Northland’s primary monitored aquifers for August 2026

Soil Moisture

Summary of modelled soil moisture data from Earth Sciences NZ

• The soil moisture deficit is calculated based on incoming daily rainfall (mm), outgoing daily potential evapotranspiration (mm), and a fixed available water capacity (the amount of water in the soil 'reservoir' that plants can use).  
• Soil moisture is above average with recent rain and is at field capacity throughout Northland, except for Dargaville (Kaikohe AWS has had missing data during this period). 

Figure 8: Calculated daily soil moisture values at key areas around Northland, courtesy of ESNZ, data ending 31 August 2026.

Climate Outlook for September - November 2026

Summary of climate forecasts from Earth Sciences NZ 

Seasonal Climate Outlook September - November 2026 | Earth Sciences New Zealand | NIWA

• El Niño conditions persist in the tropical Pacific atmosphere and ocean, according to criteria assessed by Earth Sciences New Zealand. The event by all measures has strengthened considerably during this month; especially since mid-winter; impacts on Northland’s weather patterns are starting to be felt and will persist through this outlook period.  
• Peak El Niño conditions are most likely to occur either in late spring or early summer, with the potential for this event to have significant impacts. It is likely to peak as one of the strongest in recent history, as anticipated over the last few months. The event is comparable to 1997 and has shown the strongest warming trend on record.  
• Spring will provide greater temperature ranges; air flow patterns are expected to continue to tend westerly and provide active windy conditions. Continued below normal rainfall in Northland is increasingly likely which will translate to below normal groundwater recharge creating challenges for water reliant sectors. The periods of active weather are expected to be more pronounced in 2026; depending on location and strength of high-pressure systems.     
• Temperatures are likely to be above average (50% chance).    
• Rainfall totals are most likely to be below average (50% chance). 
• Soil moisture levels and river flows are about equally likely to be below average (45% chance) or near average (40% chance). 

Table 1: Forecasted likelihood of above, near or below average climate conditions for Northland from September - November 2026.

(Expressed as % likelihood).