WorkSafe provides practical support through a Guidance Note for dealing with heat illness and related health and safety problems at workplaces.  The guidance contains recommended actions and measures to prevent or minimise the likelihood of heat illness from working outdoors in hot weather or where heat is generated as part of work.  Heat, whether 'seasonal' or part of the 'normal work environment', can be a hazard - working in heat can lead to workers suffering serious illness and can also lead to increased accidents.  Here's information on the effects of heat and an Action Plan on how to tackle the issue at work.