Maps of average annual rainfall, temperature and several other climate variables have been produced for all of New Zealand, based on the 30-year period 1981–2010.
These are useful for tasks such as identifying locations suitable for growing particular crops, assessing solar and wind power potential, or comparing very dry years with the long-term average.
The issue
The climate station data used as the basis for these maps are available from our online database DataHub.
However, in many situations a map is a much more useful source of information. For example, if you are trying to identify areas suitable for growing a particular crop. In situations like this when you are looking for a location with certain characteristics, then trawling through every station isn't practical and maps of the median annual rainfall, or the 20th or 80th percentiles, are a great way to quickly hone in on an area of interest. Then, if needed, more detailed site data can be accessed from DataHub.
NIWA has now produced these maps for all of New Zealand, based on the latest 30-year climate normal period: 1981–2010.
The approach
Long-term monthly, seasonal and annual statistics (the median, 20th and 80th percentiles) of 15 climate variables were calculated from data recorded at climate stations located throughout the country for the period 1981-2010. The variables are:
- growing degree days (base 5°C and 10°C)
- heating degree days
- potential evapotranspiration
- solar radiation
- rainfall
- rain days
- relative humidity
- days of soil moisture deficit
- sunshine hours
- average daily temperature
- average daily maximum temperature
- average daily minimum temperature
- earth temperature
- wind speed.
The station median, 20th and 80th percentile data were interpolated onto a regular 500m grid. These standard data points were then imported into a GIS package and exported as the National and Regional climate maps.
An analysis of the mapping error
The data were interpolated onto the New Zealand Map Grid projection using a thin-plate smoothing spline interpolation routine. We have performed a detailed analysis of the spatial interpolation model prediction error, based on maps produced for the previous 30-year climate normal period: 1971-2000.
Download the analysis (PDF 3.1 MB)
The maps
National and Regional monthly, seasonal and annual climate maps have been produced for each climate variable and each statistic (median, 20th and 80th percentiles), making a total of 10,672 maps produced. Samples of these maps are shown here on the following National and Regional pages (or use the menu on the left of this page):
- National
- Northland
- Auckland
- Waikato
- Bay of Plenty
- Gisborne
- Hawkes Bay
- Manawatu
- Taranaki
- Wellington
- Nelson-Marlborough
- Tasman
- West Coast
- Canterbury
- Otago
- Southland
Accessing the GIS data
GIS data raster files corresponding to these climate maps are available here.
