UV and ozone

This is the home for NIWA's UV and ozone research, including maps and graphs showing daily predictions and measurements for UV levels across New Zealand.

UV Index at Lauder

Today's UV index at Lauder

UV forecast graph
See all our UV forecasts

This information is provided by NIWA free of charge and can be used only for personal use. Repackaging and on-selling in any form is prohibited.

What is the UV Index (UVI)?

The UV index is a standard measurement of erythemal (sun-burn causing) UV intensity that gives a more objective measure than the old “time to burn” (which cannot account for skin tone). The scale is open-ended, but a UV index of greater than 10 is extreme and a UV index of less than 3 is low. For clear skies, the UVI depends mainly on the sun elevation angle and the ozone amount - see the UVI versus Sun Angle and Ozone Amount graph below.

UVI versus Sun Angle and Ozone Amount (PDF 16 KB)

The UVI also depends on cloud cover, sun-earth separation, altitude, pollution, and surface reflections (e.g., snow cover). The highest values in the world occur in the tropics at high altitudes, where the UVI can exceed 25. The geographical and seasonal variation in peak UVI for New Zealand can be viewed below. In the NZ winter, the UVI rarely exceeds 3. Because of differences in ozone, sun-earth separation and pollution, the peak UVI in NZ is approximately 40% greater than at comparable latitudes in the Northern Hemisphere.

Geographical and seasonal variation in peak UVI - NZ (PDF 16KB)

Current UVI at specific New Zealand sites

Graphs showing predicted and measured UV Index at several sites in New Zealand at which data from UV monitors maintained by NIWA are updated at 15 minute intervals. Model predictions including forecast cloud effects are included.

NIWA UV Measurements (DOC 103KB)

New Zealand ozone and UVI maps for noon (12:00NZST, 0:00GMT)

The maps provided here are forecasts modelled on available satellite ozone data.

Yesterday UV Index Clear Sky Ozone
Today UV Index Clear Sky Ozone

Yesterday's UVI measured at specific sites in New Zealand and the South Pacific

Graphs showing predicted and measured UV Index at Leigh, Paraparaumu, Christchurch, Lauder, Invercargill and Rarotonga are updated daily.

Predicted and measured UV Index

Today's UVI forecasts for specific sites

Graphs showing UVI forecasts specific sites in New Zealand and the South Pacific region. When the UVI is low (less than 3), no protection is required and short exposures to sunlight will be beneficial for vitamin D production. At all other times some protection to avoid sunburn is recommended. The "UV Sun Protection Alert Period" is defined as the period when the clear sky forecast is greater than UVI = 3, a level at which damage to fair skin can occur in less than 1 hour. When the UVI = 12, damage to fair skin can occur in less than 15 minutes. For darker Polynesian skin types the safe exposure periods can be doubled. Further details on UV and health are provided by the Cancer Society's Sunsmart and Sunsmart Schools and by the Health Sponsorship Council .

UVI forecasts specific sites in New Zealand and the South Pacific region


Sunsmart Schools 

Health Promotion Agency  

Lauder Ozone

A graph of daily ozone measurements at Lauder over this year compared with past years (climatological variability). Ozone column amounts are measured in Dobson Units (DU), where 1 DU = 2.69 x 1016 molecule/cm2 

Data availability

  • Ozone, cloud transmission, total radiation and various biological weightings of UV radiation can be extracted for approximately 100 sites in the New Zealand region using the NIWA UV Atlas.

  • NIWA UV Atlas

  • Erythemally-weighted UV irradiances (UV Index values) from Lauder and several other sites in the New Zealand region can be extracted from the NIWA Climate database. Select Datatype/Daily and Hourly Observations/Sunshine and Radiation/UV radiation to access historical 10-minute mean UVI values. These data are available from the same sites as plotted above for Yesterday's UVI, as specified in the site-selection menu.

    NIWA Climate database

  • UV radiation data (and trace gas data) from Lauder compared with other global sites can be accessed from the international Network for the Detection of Atmospheric Composition Change (NDACC).

  • Other radiation data, including aerosol optical depths from Lauder compared with other global sites can be accessed from the international Baseline Surface Radiation Network.

    Baseline Surface Radiation Network 

  • UV data from Lauder compared with other North American locations can be accessed from the US Department of Agriculture. 

    US Department of Agriculture 

Assessments of ozone depletion and its effects

NIWA scientists contribute to regular international assessments of ozone depletion and its environmental impacts, as required under the terms of the Montreal Protocol on Protection of the Ozone Layer. These assessments include responses, in simple layman's terms, to Frequently Asked Questions (FAQs).

Montreal Protocol on Protection of the Ozone Layer 

The NIWA UV Atlas

The aim of the UV Atlas project is to produce maps and time series of parameters describing the UV radiation environment over New Zealand since 1960. Maps are produced for the area around New Zealand (34° to 48° S, 166° to 180° E), and time series are produced at sites where broadband radiation measurements are available. Click for more information on the:

  • outputs produced by this project

  • details on how to obtain the data

access to data viewing software and its documentation. 

Find out more NIWA UV Atlas

NIWA UV Spectrometer Systems

NIWA has been engaged in an active UV Research Programme since the 1980's. The cornerstone of this work is the routine accurate measurement of the spectrum of surface UV irradiance to quantify UV climatologies, to understand the causes of UV variability (temporally and spatially), and to monitor long-term changes. Read more about NIWA's UV spectrometer systems here

NIWA UV spectrometer systems

Personal UV Dosimeters

There is widespread public interest in the relationships between UV radiation and health. The effects of UV on health can be harmful – as in its effect on skin cancer rates, or beneficial – as in the case of its effect on vitamin D status. In the past, researchers have attempted to determine these relationships as functions of ambient UV radiation. However, the UV doses that humans are typically receive are less than 5% of that available UV.

More about personal UV dosimeters

Latest All-Sky Image at Lauder, New Zealand

The all-sky image shows a hemispheric view of the sky at Lauder. These images record the cloud cover at Lauder for use in the atmospheric radiation research. The images are updated every 10 minutes and an archive image is available for each of the last 24 hours.

All-sky image

Further information 

uv2Day smartphone app 

NIWA data has been used recently in the development of a UVI app - "uv2Day". The app provides forecasts of the UV Index (UVI) - with and without cloud effects - throughout the day at the nearest location, or at other selectable locations within the New Zealand, Australia, South Pacific region, including Antarctica. The app includes behavioural messages, and is useful for planning activities to optimise sun exposure throughout the year, and for educating the public on what theUVI means. 

Note: This app is not a NIWA product.

View the app in the Google Play store 

View the app in the iPhone app store


The GlobalUV app

This app provides estimates of the current UVI and how it is expected to vary throughout the day at any location throughout the globe. It also provides behavioural advice on how long you can remain in sunlight before damage occurs for your selected skin type. It is an educational tool that helps you plan your day to optimise your UV exposure.

The app is an extension of the uv2Day app (developed in collaboration with NIWA) which applies only to the Pacific region, where aerosol extinctions are small. Unlike that app, GlobalUV uses forecasts of ozone and cloud effects to calculate UVI on the fly. At a small cost in speed, there is a huge benefit in versatility. In addition, it provides information about position, altitude, sun elevation angle, ozone amounts, aerosol extinctions, and effects of clouds and surface reflectance (e.g., due to snow cover). Additionally it shows the current global pattern of UVI. Finally, it can display clear-sky UVI values for other seasons at any location. Currently, it is available only for android phones.

View the app in the Google Play store.

See here for further details.

Note: this app is not a NIWA product. 


UV radiation sensors on the roof of the optics building at Lauder. [NIWA]