Hawke’s Bay has been shaping up as one of the driest regions through late spring and early summer but rainfall later in December and early January has given some relief. Elsewhere, all regions have had periods of very warm and sometimes hot conditions but also prolonged cloudiness and cooler weather. Parts of Central Otago fell uncomfortably close to freezing on 21 December and, at the time of writing, the temperature at Gibbston Valley has not reached 30C this summer. The cool periods have not been as unceasingly cold as the first half of summer 2024-25, but it has felt like summer has been checking out at times. This has been the result of an increased easterly flow that is to be expected during a La Niña. Thunderstorm activity appears to be higher than usual this summer and we await end of season statistics to confirm whether this was the case.
Sea surface temperatures around New Zealand remain above the long term average and contribute to more available moisture and energy when rain bearing systems cross our shores. Heatwave conditions for Hawke’s Bay and Gisborne went very close to January temperature records. This shows that even though certain synoptic conditions (warm northwest airflow originating from Australia) become less frequent during different La Niña climate cycles, they
can still occur, and produce extreme conditions outside of the usual northeasterly stereotype.
There is a growing conversation around the world that La Niña will fade quickly this year and that 2026 will see the return of an El Niño. This is likely to have implications on our weather for spring later in the year but I won’t get ahead of things. La Niña is still with us and will continue to affect the weather around New Zealand through the remainder of summer and into autumn.
Outlook for February and March:
Gisborne/Hawke's Bay - The east coast of the North Island is one of the front lines when moisture-laden air arrives from the tropics. Even with a weakening La Niña, a predominant easterly flow is expected to continue through February. This flow may become less consistent during March, with a return to westerly conditions at times. Mean temperatures are likely to run a little above average, especially through March. There remains an increased risk of a tropical low or ex-tropical cyclone bringing a significant rain event. Rainfall totals are likely to be above average, along with elevated humidity and dew points at times. Daytime maximum temperatures may run close to or even below average at times, but nighttime minimums remain above average.
Wairarapa - Summer has not been particularly warm overall for Wairarapa, apart from a period of milder temperatures during early December and early January. The easterly conditions have tended southeast at times over the lower Noth Island and this is likely to continue in the short term. Milder temperatures may develop during February as the southern part of the North Island becomes more influenced by high pressure south of New Zealand. Temperatures are likely to remain close to average through until Easter but may push above average at times through March, as a milder north to northeast flow develops. Rainfall totals remain close to or above average and there is still an increased risk of a heavy rain evening affecting the lower North Island.
Nelson - The upper South Island is placed in a zone of uncertainty, where the seasonal rainfall totals can be strongly influenced by warm and cold air convergence as well as the movement of frontal systems that originate either from the Tasman Sea or the subtropics. A reasonably settled end to summer and start to autumn is likely, with near or slightly above average temperatures. Rainfall totals look to be close to average, but there remains an increased risk of localised heavy rain from thunderstorms. Any major rain events are likely to be dictated by the path of low pressure systems moving south onto New Zealand and a return to northwest conditions later in March.
Marlborough/North Canterbury - La Niña generally produces cloudier than average conditions for eastern regions and this is likely to remain the case for most of Marlborough and for North Canterbury. Sunshine totals are likely to be reduced under a continuing easterly flow through early February and this is also likely to impact daytime maximum temperatures for prolonged periods. Temperatures are still likely to run near average and could push above average again later in February and through March as north westerlies begin to make a return during early autumn. Rainfall totals are likely to be close to average, but there may be periods of dry conditions across Marlborough. Humidity levels remain elevated through early February but should be closer to average during March. There remains an increased risk that an ex tropical system will bring high humidity and a prolonged period of wet conditions.
Central Otago - Conditions are likely to become reasonably settled through February, with a larger diurnal range in temperature between overnight minimums and daytime maximums. Rainfall is expected to be below average through February. As the influence of high pressure weakens through March there is likely to be an increase in northwest conditions and rain bearing fronts may bring precipitation to the lower South Island as well as fluctuating temperatures. Winds remain lighter through February, but March is expected to be a windier month.
Better Decisions with Good Information
Quality weather data is an incredibly important part of understanding weather and climate, from global forecast models down to the minimum temperature and seasonal rainfall across vineyard or individual blocks.
As someone who has studied climate and weather for most of my life, I have seen how good quality and poor quality data can influence decision making. Poor quality weather stations can give information that does not accurately represent the weather in a particular area and leads to assumptions and guesses when making critical decisions. Good quality weather data means that critical decisions can be made with much more confidence and the risks are reduced.
The first part is an accurate weather station. There are many inexpensive weather stations on the market and they often claim to be able to provide a plethora of information for the owner. These weather stations often lack in quality sensor calibration and there is a greater variation or margin of error. This can lead to unrealistic expectations or impressions of the weather outside and how it might be affecting a crop. Higher quality weather stations and sensors will cost more but they will give you a more accurate representation of the weather outside in the vineyard.
The second part of the equation is the placement of the weather station. It is not always easy to find the ‘perfect’ spot for a weather station. International standards demand the temperature sensors to be 1.2 metres from the ground and in a well shielded screen as well as being at least 10m from any building or obstruction. Rain gauges should ideally be only 30cm from the ground, as being higher means that rain blown around by the wind may not be captured.
Setting up the perfect weather station in terms of componentry and location is not always attainable, but working to ensure that as many factors that can improve data collection are achieved will go a long way to creating a quality data set that can be used with confidence.
