Climate variable details


Change in Hot Days >25C
Hot Days are considered as the number of days per year equal to or exceeding 25°C.

More details

Climate variable details

Change in Hot Days >25C

High temperature extremes (i.e. ‘hot days’) are considered as the number of days per year where the max temperature is equal to or exceeds 25°C.
At 2040, eastern areas are projected to experience increases of about 10-20 days per year for RCP4.5 and 10-30 days for RCP8.5. For western areas, an increase of up to 10 hot days per year is projected.
At 2090 under RCP4.5, hot days are expected to increase by 30-40 days per year in the east. Western areas are projected to experience mostly 5-10 more hot days per year. Under RCP8.5 at 2090, large increases in the number of hot days across most of the region are projected. For central Wairarapa, the number of hot days is projected to increase by around 70 days per year. Western areas are projected to experience an increase of around 30-40 days in lowlands, decreasing to 5 days per year for the highest elevations.

See details in report.

Other sources of information

How to use this page

Change map content

  • Use the Climate Variable dropdown to choose from 1 of 21 available variables
  • Use other dropdowns to choose the required period, RCP, and season values
  • Note not all variables have seasonal values, some are annual only
  • Click on the Update Map button to refresh the map, legend and associated descriptive text

Other tools

  • Click on the map to view the modelled value at any location
  • Click on the search tool and enter a name to find any placename in the map area
  • Click on the layer control tool and choose an option to change the basemap type or overlays

Background to this page

Background

This webpage displays a set of map layers which illustrate the predicted impacts of climate change in the Wellington Region. Data was supplied with a report commissioned by GWRC from NIWA dated August 2017.

RCP

It shows predicted changes at 2040 and 2090 for a range of four RCPs (2.6, 4.5, 6.0 and 8.5). All changes are in relation to the 1986-2005 base climate. Each RCP (Representative Concentration Pathway) is a modelled scenario for how greenhouse gas emissions could evolve over the rest of this century. RCP8.5 is a high emissions scenario, RCP4.5 and 6.0 are intermediate scenarios, and RCP2.6 is a very low emissions scenario.

Report

The report can be downloaded from the GWRC website as a summary or full report.

ARC climate projections

Please also note that the new IPCC AR6 projections (SSP scenarios) are now becoming available (https://niwa.co.nz/climate-and-weather/climate-change-scenarios-new-zealand). These new modelled projections are not meant to replace the ones we have, but rather to complement them, ideally being used in conjunction with our existing tools. GWRC has commissioned a new report by NIWA (to be released in early 2025) to address the regional differences, and help build our understanding of nuance and uncertainty involved with each climate variable going forward.

Please note

Please note these results are based on modelled data, and as such they are indicative only of likely changes, depending on future greenhouse gases emissions.
The nominal resolution is 5 x 5 km. The zoom tool should be used with care, as the data is best interpreted as a broad spatial pattern. For coastal areas with no data, a direct extrapolation of the values immediately adjacent is appropriate. All fields are a result of an average of six IPCC models regarded by NIWA as adequately describing New Zealand climatic variability.

Scenario choice

It’s impossible to know which scenario will be closer to reality by the end of the century, and therefore it is recommended that people’s planning incorporates a range of outcomes. The latest data (as of 2017) shows that even if all the pledges countries made under the 2015 Paris Climate agreement were fulfilled, global emissions could still be on a high-intermediate path not much lower than RCP8.5. Each country is required to update its pledge every five years, enabling the international community to improve emissions reduction commitments over time.