Patients dialling 999 in a heatwave could have to wait for temperatures to drop before an ambulance arrives under union plans to stop crews working in hot weather. Unison says many emergency workers are expected to work in conditions 'harmful to their health' and wants NHS trusts to do more to protect members during increasingly hot summers. This has occurred during shifts where staff have queued for hours outside hospitals to hand over patients, 'often in temperatures exceeding 30C'. The union Unison says it 'backs the introduction of a maximum working temperature during increasingly frequent periods of extreme heat'. 'The union also backs the introduction of a maximum working temperature during increasingly frequent periods of extreme heat,' it adds.