Radar

The radar page shows a live, animated rain radar composite for the South Island, provided through the RainViewer tile service and drawn natively on this page for speed. It lets you track showers, fronts and thunderstorms in near real time and see how they have moved over the past couple of hours.

How to read the radar

Weather radar sends out pulses of microwave energy and measures what is reflected back from rain, snow and hail. The strength of the return, called reflectivity and measured in dBZ, is shown as colour on the map. Light blues indicate drizzle or light rain, greens and yellows moderate to heavy rain, and oranges and reds very heavy rain or hail.

Use the play control to animate the last few frames. The direction and speed of movement tell you when rain is likely to arrive at or clear your location. Cells that rapidly grow brighter are intensifying showers or developing thunderstorms.

Radar coverage in the South Island

New Zealand's weather radar network includes sites covering Canterbury, the West Coast, Otago, Southland and the top of the South Island. Radar beams travel in straight lines and are blocked by terrain, so the Southern Alps create shadows where precipitation can be underestimated or missed, particularly in inland valleys and at long range. Snow and drizzle also return weaker signals than rain, so they may appear lighter than they really are.

Limitations

Radar shows where precipitation is falling now, not where it will fall in several hours. Frames are typically updated every few minutes, so there can be a short delay between what the radar shows and what is happening outside. Ground clutter, sea clutter and bright-band effects near the freezing level can also produce false or exaggerated echoes.

South Island Met Agency is an independent private forecaster and does not issue official government severe weather warnings. For official New Zealand watches and warnings, visit MetService. Read our About Us & Terms and Privacy Policy.