MetService weather warnings explained: watch, warning, orange and red
New Zealand's alert system decoded - what a Watch means, what a Warning means, and why the colour matters.
MetService, New Zealand's national weather authority, runs a two-tier alert system. A Severe Weather Watch means dangerous weather is possible but not yet certain; a Severe Weather Warning means it is expected or already happening. Warnings carry a colour - Orange for significant, disruptive conditions and Red for the most extreme, potentially life-threatening events. Only MetService is legally mandated to issue them.
Who issues weather warnings in New Zealand?
Under the Meteorological Services Act 1990, MetService is the sole body designated to issue official severe weather watches and warnings for New Zealand. That legal status matters: while plenty of apps, websites and private forecasters offer their own outlooks, only a MetService warning triggers the official emergency-management response from Civil Defence, regional councils and NZTA Waka Kotahi. When you hear a warning quoted on the news, it has come from MetService.
MetService pairs its warnings with input from agencies such as NIWA on climate context, but the operational warning itself is MetService's call. It is issued for three main hazards - heavy rain, heavy snow and severe wind (gales) - and, separately, for other threats such as thunderstorms and, via partner agencies, coastal and marine hazards.
MetService operates as a state-owned enterprise and forecasts around the clock, feeding the same warnings to Civil Defence, the media, roading authorities and the public simultaneously. That single, authoritative source is deliberate: in a fast-moving event you do not want competing official numbers, so the country funnels its severe-weather alerting through one national forecaster.
Watch versus Warning: what's the difference?
The single most useful thing to understand is the escalation ladder. It runs from a broad heads-up to a firm, imminent alert:
- Severe Weather Outlook - issued up to about six days ahead, flagging where severe weather might develop. This is a "keep an eye on it" signal.
- Severe Weather Watch - conditions are becoming favourable for severe weather, but confidence or exact location is not high enough to warrant a warning. Severe weather is possible.
- Severe Weather Warning - severe weather is expected. This is the point to act: warnings are issued when forecast rainfall, wind or snow is likely to reach criteria that cause real disruption or danger.
Think of it as possible (Watch) versus expected (Warning). A Watch can be upgraded to a Warning as a system firms up, downgraded, or cancelled entirely if the threat fades.
What do Orange and Red warnings mean?
MetService moved to an impact-based, coloured warning system in 2019 so that the alert reflects likely consequences, not just millimetres or wind speed. Two colours apply to warnings:
- Orange Warning - the standard warning level. Expect significant impacts: surface flooding, slips, difficult driving, possible power cuts and disruption to travel. Most severe weather warnings issued in a typical year are Orange.
- Red Warning - the top tier, reserved for the most extreme events. A Red Warning signals conditions rarely experienced, with the potential for widespread damage, threat to life and major disruption. It is a call to act immediately and follow instructions from Civil Defence.
Red Warnings are deliberately rare - MetService keeps them for exceptional situations so the public takes them seriously. Cyclone Gabrielle in February 2023 was accompanied by Red rain warnings across the North Island's east, one of the highest-profile uses of the top tier since it was introduced. Overusing the top colour would blunt its meaning, so the threshold for Red is set high on purpose, and its appearance should be read as a genuine call to change your plans.
What weather types trigger a warning?
Warnings cover the hazards most likely to cause harm in New Zealand's terrain. The indicative thresholds below are the broad national criteria MetService publishes; the exact trigger is tuned region by region, because the same rainfall means very different things in the steep Tararua Range versus flat Canterbury.
| Hazard | Indicative warning basis | Typical impacts |
|---|---|---|
| Heavy Rain | Rainfall approaching or exceeding roughly 100 mm in 24 hours (lower in flood-prone terrain) | Surface flooding, rising rivers, slips, road closures |
| Severe Gale / Strong Wind | Mean winds near 90 km/h or gusts near 110 km/h in populated areas | Downed trees and lines, power cuts, dangerous driving |
| Heavy Snow | Significant snow accumulation near populated areas or key routes | Road closures, stock losses, isolation |
Thunderstorms are handled separately through a Severe Thunderstorm Watch/Warning stream, and marine and coastal hazards through dedicated forecasts. Always read the plain-language impact statement in the warning text - the number is only half the story.
How the colours map to action
The point of the colour system is behaviour. Orange means prepare and adjust your plans - delay non-essential travel, secure loose items, check on neighbours. Red means the plan changes now - avoid travel, be ready to evacuate if told to, and treat official instructions as non-negotiable. Because the colour reflects impact rather than a raw measurement, a moderate rainfall total in a saturated catchment can justify a higher colour than a larger total on dry ground.
How to read a warning like a forecaster
A warning tells you the official position; it does not tell you how confident that position is. That is where comparing forecast models helps. checkweather lines up the three global heavyweights - ECMWF, GFS and ICON - and turns their agreement or disagreement into a plain-English confidence score, then grades an accuracy scoreboard against what actually happened. When those models are tightly clustered behind a MetService Orange or Red warning, you can treat the timing and location as solid. When they diverge, expect the warning area or timing to shift as it is updated. Used together, the official warning and the model spread give you both the call and the confidence behind it.