There's no legal maximum temperature — but there is a duty to manage the risk
The HSWA does not set a maximum workplace temperature, but it does require you to manage the risk of heat-related illness so far as is reasonably practicable. Heat strain builds from more than air temperature — humidity, radiant heat, work rate and clothing all matter — and untreated it runs from heat stress to heat exhaustion to heat stroke, a medical emergency. The reliable controls are the simple ones, in order: cool the environment first, then water, rest and shade.
The HSWA is not prescriptive about temperature — it does not name a figure at which work must stop. Instead, the primary duty of care requires you to identify the risk of working in heat (and cold) and manage it so far as is reasonably practicable.
Recognising thermal discomfort and stress, and raising it early, matters for both businesses and workers. Through consultation with your workers and their health and safety representatives, you can agree the conditions under which work will be paused or changed.
Sweating is the body's main way of staying cool. When it can't shed heat fast enough, core temperature rises and heat illness sets in — and along the way, concentration and coordination drop, which raises the risk of other incidents.
It typically progresses in stages: heat rash and cramps; then heat exhaustion — heavy sweating, dizziness, nausea, headache and weakness; and if it isn't treated, heat stroke — confusion, collapse, and hot or clammy skin. Heat stroke is a medical emergency: call 111, move the person to a cool place and start cooling them while you wait.
Air temperature is only part of the picture. Several factors combine to determine how much heat a worker is under.
| Factor | Why it matters |
|---|---|
| Air temperature | The obvious one — but rarely the whole story. |
| Humidity | High humidity stops sweat evaporating, so the body cannot cool. |
| Radiant heat | Sun, furnaces, ovens, hot plant and asphalt add heat directly. |
| Air movement | Still air traps heat; airflow helps sweat evaporate. |
| Work rate | Hard physical work generates large amounts of internal heat. |
| Clothing & PPE | Heavy or non-breathable gear traps heat and adds to the load. |
| The person | Fitness, age, health conditions, medication, hydration and acclimatisation. |
Work down the hierarchy. Deal with the heat source and the environment first; treat water, rest and rotation as the dependable backbone; and use PPE last.
Reduce or shield radiant heat sources, improve ventilation and exhaust, use air conditioning where practical, insulate metal-clad buildings, and fit blinds or reflective coatings to cut direct sun. Outdoors, provide shade and reschedule the hottest tasks to cooler parts of the day.
Make cool drinking water available and encourage frequent small drinks, schedule rest breaks in cool or shaded areas, rotate and pace work, shorten shifts in extreme heat, and acclimatise new or returning workers over several days. Use a buddy system, train people to spot the symptoms in themselves and others, and build it into a heat or temperature management plan agreed with workers and HSRs.
Where heat remains, use light, breathable clothing, cooling vests, and sun protection — making sure PPE does not add more heat load than it removes.
Outdoor heat is harder to control, and it comes with ultraviolet (UV) exposure as well — a serious risk given New Zealand's high skin-cancer rates. Combine heat controls with sun protection: shade, timing work away from the peak of the day, and hats, clothing and sunscreen. Pair this guide with fatigue management, since heat and long hours compound each other.
The same duty applies to working in the cold. Provide layered clothing, climate-controlled shelter away from wind and rain, drying facilities for wet gear, and warm drinks, and train workers to recognise cold-related illness in themselves and their workmates.
Record your heat risk assessment, controls and management plan in one place. Book a demo and we'll show you how it works — free 30-day trial included.
No. The HSWA is not prescriptive and does not set a temperature at which work must stop. You are required to identify and manage the risk of working in heat so far as is reasonably practicable, and you can agree work-pause conditions with workers and HSRs.
Heat exhaustion involves heavy sweating, dizziness, nausea and weakness, and usually responds to cooling, rest and fluids. Heat stroke is far more serious — confusion, collapse, and hot or clammy skin — and is a medical emergency: call 111 and start cooling the person immediately.
Work down the hierarchy: cool the environment and shield heat sources first, then manage the work with water, scheduled rest in cool areas, rotation, pacing and acclimatisation, and use light, breathable PPE last.
No. Humidity, radiant heat, air movement, how hard the work is, and clothing all affect heat strain, along with personal factors like hydration and acclimatisation. Assess the whole picture, not just the thermometer.
Yes. The duty to manage thermal risk covers cold as well as heat — with controls such as layered clothing, sheltered warm break areas, drying facilities and training to spot cold-related illness.
