A road cone doesn’t read the forecast. The crew setting it out had better. Earth Sciences New Zealand’s seasonal outlook for October to December 2026 says very strong El Niño conditions are present in the tropical Pacific and are expected to strengthen further.
For New Zealand, that means more frequent westerlies with increased wind strength and gustiness, according to the outlook. It expects more fronts in the west and south, dry and warm föhn conditions in the east, and temperatures most likely above average across most of the country. On the West Coast, Southern Alps, inland Otago and Southland, rainfall has a 55% chance of being above normal, with an increased potential for heavy rain events and unusually strong winds.
Earth Sciences NZ expects El Niño to peak in late spring or early summer and says the event is likely to rank among the strongest on record. It also warns that El Niño doesn’t rule out the odd northerly flow bringing heavy rain to parts of the country.
All of this lands as traffic management moves to a new rulebook. NZTA’s New Zealand guide to temporary traffic management (NZGTTM) is now its preferred guidance, and NZTA stopped updating the old Code of Practice (CoPTTM) from 1 November 2024.
Road controlling authorities set their own switchover dates. Auckland Transport has assessed all new corridor access requests under NZGTTM since 1 July 2026 and moves existing traffic management plans across from 1 July 2027, while South Wairarapa and Carterton district councils stopped accepting CoPTTM-based plans from 1 July 2026.
The guide is risk-based, so there’s no table telling you which layout to use in a southerly. NZTA says each site must be assessed individually. When contractors describe a site’s context during planning, the guide lists the natural environment, including weather, as one of the things that may affect the activity.
WorkSafe’s guidance for road and roadside work lists strong gusts moving traffic management signage among the risks of high wind. “Large objects (such as TTM signs) can act as a sail in high winds,” the guidance says. It recommends avoiding carrying them in those conditions, or giving workers extra help.
Its controls include securing signage, considering helmets, and holding loose items down with weights, ropes, chains or stakes, after checking for underground services first. WorkSafe also lists stopping work when high winds make it dangerous, keeping clear of high-sided vehicles that gusts can topple, and not working at height when high winds are forecast.
The wind doesn’t knock off when the crew does. NZGTTM says installed devices must keep operating as designed during inactive hours, and that conditions such as high wind or winter snow may need more frequent checks. Daily site records should include the weather conditions and confirm signs are upright, clean, visible and correctly spaced.
WorkSafe’s first control for extreme conditions is to get accurate condition reports and reschedule non-essential work for when conditions improve. Even for essential work, it says workers shouldn’t start until the business has managed the risks to a reasonably practicable level. Crews should have the knowledge, experience and authority to stop work if they believe conditions have become unsafe.
MetService runs the official warning system. A Watch is typically issued two to three days before a potential severe weather event, and warnings typically 24 hours out. An Orange Warning means take action as appropriate, while a Red Warning, reserved for the most extreme events, means immediate action is required and people should follow official advice.
The January 2026 storms on the Coromandel showed what that looks like on the network. With a red heavy rain warning in place, NZTA had nine crews out assessing roads, clearing debris and watching flood waters, and asked drivers to watch for contractors clearing hazards and to drive slowly through work sites.
NZGTTM treats floods, crashes and emergency road repairs as time-critical reactive work, where responders do the best they can with what they have. After the first response, it expects all parties to move to a planned response as quickly as possible, and notes a major storm may need months in the long-term response phase.
WorkSafe adds a check-in system so managers always know where workers are, and an emergency plan that covers alternative routes if the planned one is cut off. Low visibility in heavy rain or fog affects stopping distances and raises the risk of workers being hit, WorkSafe says. NZGTTM asks crews to check regularly that signs and devices still have good low-light visibility and reflectivity.
The outlook’s warmer east brings the other extreme. WorkSafe lists standing on hot road surfaces, asphalt and emulsion work, and heavy PPE among the conditions that push body temperatures to harmful levels, and says heat-related illness can be fatal if ignored.
Its controls include scheduling work for cooler times of the day, rotating workers often, and allowing extra rest breaks in climate-controlled rest areas. WorkSafe also recommends keeping cool drinks available at all times, making sure workers are acclimatised, and choosing PPE that’s as light and breathable as possible without losing its protective function.
WorkSafe wants workers trained to spot the signs of heat illness in themselves and their workmates. The tropical cyclone season formally begins on 1 November, Earth Sciences NZ notes, so the outlook is worth a look before the next site plan is signed off.
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