The short answer is: it depends. And so is the long answer, but it’s worth understanding it before you spend a whole week sweating in front of your computer without knowing what you’re entitled to.
Swiss law does not specify a maximum temperature at which work is automatically suspended. However, Ordinance 3 relating to the Labour Act (OLT3) requires employers to ensure that working conditions do not put their employees’ health at risk. When the temperature at the workplace consistently exceeds 28 degrees, the employer is legally obliged to take action: ventilation, additional breaks, rescheduling of working hours, and access to water. This is not a recommendation. It is an obligation. If the employer fails to do so, the cantonal labour inspectorate may intervene. For outdoor work, on building sites or work involving heavy physical labour, many collective agreements provide for mandatory breaks or even the suspension of work above certain thresholds, which vary depending on the sector and the canton.
The reality in many companies is that the system doesn’t kick in automatically. The employee has to raise the issue. If the temperature at your workplace exceeds 30 degrees and your employer does nothing, the first step is to speak to them directly. If you get no response, you can contact the cantonal labour inspectorate or the trade union for your sector. Each canton handles this slightly differently, and collective agreements add further layers of protection depending on the type of work. Many people only realise this after having put up with the situation for a week without saying anything.