Heat waves are no longer an exceptional phenomenon. In France, high temperatures are increasingly a real occupational risk. This is especially true for construction, public works, agriculture, logistics, industry and seasonal work.
The employer must prepare accordingly. It should assess the risks beforehand and implement protection measures. It's not just about employee comfort. Their health and safety are crucial.
According to art. L.4121-1 Code du travail, the employer must ensure the safety and protect the health of employees. This includes prevention, training and proper work organisation.
From 2025, the regulations have been strengthened. Decree n° 2025-482 of May 27, 2025 introduced special rules for protection against heat. The employer must treat high temperatures as a risk. He should evaluate, document and limit them.
Heat as an occupational hazard
High temperatures can cause dehydration, fatigue and dizziness. In extreme cases, it leads to heat stroke. The heat also increases the risk of accidents. It lowers concentration and slows reactions.
The risks are for outdoor and indoor work. Especially when heat accumulates. Art. R.4463-2 Code du travail obliges the employer to assess this risk.
If the risk is significant, the employer must take action. He should link them to an occupational risk assessment. If necessary, they should be included in DUERP.
Working indoors
The employer must ensure that the workplace is at an appropriate temperature. This follows from Art. R.4223-13 Code du travail.
This does not mean that it is mandatory to install air conditioning. However, the employer should limit the risk of overheating. It can use ventilation, blinds or shading. Improving air circulation and reducing heat sources also helps.
It is worth providing cooler rest areas. Work must also be organized in such a way as to reduce the residence time at high temperature.
Outdoor work and construction sites
Outdoor workers require special protection. This applies to construction, agriculture and road works.
The employer should adapt the organization of work. The toughest tasks should be planned for colder hours. More frequent breaks and task rotation also need to be introduced. Access to shaded areas is important.
Water is key on the construction site. Art. R.4534-143 Code du travail imposes an obligation to provide it. If there is no running water, the employer must provide at least 3 liters per day per person.
Art. R.4225-2 Code du travail confirms the general obligation to provide drinking water.
What preventive measures should the employer implement?
Art. R.4463-3 Code du travail indicates preventive actions. The employer should limit exposure to heat. It can change the organization of work and adjust working hours.
In practice, this means shifting tasks to cooler hours. You can also limit heavy work or temporarily stop it.
The employer should use technical measures. These include ventilation, shading and cooling devices. Foggers and insulation are also helpful.
The selection of equipment and PPE is important. Protection measures must not increase the risk of overheating. If necessary, the organization of work must be adapted.
Information, training and alarm procedures
Workers must be aware of the symptoms of the threat. This applies to dehydration and heat stroke. The employer is obliged to inform and train them.
It should clearly define the rules of operation. The employee must know when to stop work and to whom to report the problem. It is also important to know the first aid point.
Posted and temporary workers require special attention. You need to make sure they understand the instructions and apply them in practice.
Météo-France alerts and prefectural decisions
The Météo-France system reports heatwaves. This follows from Art. R.4463-1 Code du travail.
The employer should check alerts regularly. It must also follow the decisions of prefectures. Local authorities may introduce additional measures.
The prefecture may allow work to begin earlier. This often applies to construction. It can also reduce noise and other nuisances.
In extreme cases, work may be stopped. This applies when the threat is high.
Posted workers and subcontractors
Coordination is key. This applies to posted workers and subcontractors.
Everyone needs to know the rules of working in the heat. It is about access to water, breaks and alarm procedures.
Lack of communication reduces the effectiveness of actions. Even good procedures may then not work.
Practical checklist for the employer
Before and during heat, the employer should check:
- whether it assessed the risk associated with temperature;
- whether it has implemented preventive measures and included them in the DUERP;
- whether it provided adequate water;
- whether workers have access to rest areas; and
- whether he adjusted his working hours;
- whether he reduced heavy tasks during the hottest hours;
- whether he informed employees about the threats;
- do managers know how to react;
- whether PPEs are adapted to the conditions;
- whether he checked Météo-France alerts and prefectural decisions;
- whether he has given instructions to subcontractors.
Summary
A heat wave is a real occupational hazard. The employer must evaluate and limit them. It should also adapt the organization of work.
The most important measures are the provision of water and the change in working hours. Exposure must also be limited and employees informed.
In some sectors, prefectural decisions are important. This is especially true for construction and agriculture.
Good preparation reduces the risk of accidents. It also protects against dehydration and heat stroke.
For the employer, this means that work organisation must be prepared in advance, risks assessed and specific protection measures implemented. It is not just about the comfort of workers, but about the obligation to protect their health and safety.
According to art. L.4121-1 Code du travail, the employer is obliged to take the necessary measures to ensure the safety and protection of the physical and mental health of employees. This obligation includes preventive measures, information, training and appropriate work organization.
From 2025, these regulations have been further strengthened. Decree n° 2025-482 of May 27, 2025 introduced specific rules into the Code du travail regarding the protection of workers from the risks associated with episodes of intense heat. This means that the employer should treat high temperatures as a risk that should be assessed, documented and mitigated by appropriate measures.
Heat as an occupational hazard
Exposure to high temperatures can lead to dehydration, severe fatigue, dizziness, heat exhaustion, and in the most serious cases, heat stroke. Heat also increases the risk of accidents at work because it lowers concentration, slows reactions and makes it difficult to perform manual work.
This risk applies both to outdoor work and to work indoors if heat accumulates in them. Therefore, art. R.4463-2 Code du travail anticipates that the employer assesses the risks associated with the exposure of workers to episodes of intense heat, both indoors and outdoors.
If the assessment reveals a risk to health or safety, the employer must determine appropriate preventive measures. In practice, they should be linked to an occupational risk assessment and, where the risk is significant, included in DUERP.
Working indoors
In the case of indoor work, the employer must ensure that the temperature is appropriate to the type of work performed. This follows from Art. R.4223-13 Code du travail, which refers to the temperature in the rooms intended for work.
This does not mean that air conditioning is automatically required to be installed in every workplace. However, the employer should apply measures to reduce the risk of overheating, such as ventilation, shading, blinds, improving air circulation, limiting heat sources or reorganising workstations.
In rooms particularly exposed to heating, it is also worth providing for cooler resting places and work organization that will limit the time employees stay at the highest temperature.
Outdoor work and construction sites
Workers working outdoors must be protected from the effects of weather conditions, including heat waves. In practice, this applies particularly to construction, public works, agriculture, structural assembly, road works, seasonal works and works carried out in the open.
In these sectors, it is crucial not only to provide protection measures, but also to adapt the organization of work itself. The most physically demanding work should, as far as possible, be planned for the cooler hours of the day. The employer should also provide for more frequent breaks, job rotation, reduced work in full sun and access to shaded or cooler rest areas.
Access to water is of particular importance on construction sites. Art. R.4534-143 Code du travail provides for the obligation to provide workers with drinking and fresh water, and when there is no access to running water — at least 3 litres of water per day per worker.
Notwithstanding, art. R.4225-2 Code du travail imposes a general obligation on the employer to provide workers with fresh drinking water.
What preventive measures should the employer implement?
Art. R.4463-3 Code du travail indicates exemplary actions on which the prevention of risks related to intense heat should be based. The employer should, above all, limit exposure to high temperatures by selecting appropriate working methods, changing the organization of positions and adjusting working hours.
In practice, this means that some tasks can be shifted to cooler hours, the most physical work can be reduced, the pace of work can be reduced or activities that pose too great a risk under given conditions can be temporarily suspended.
The employer should also apply technical measures to limit the heating of workplaces. This may include ventilation, shading, cooling devices, foggers, insulation or repositioning of stations.
The selection of appropriate work equipment and personal protective equipment is also very important. PPEs should protect the worker but must not at the same time excessively increase the risk of overheating. If the use of helmets, protective clothing, gloves or other protective measures is necessary, the employer should adapt the work organization to limit the heat load.
Information, training and alarm procedures
The employee should know how to recognize the first signs of danger. This is especially true for dehydration, heat exhaustion and heat stroke. Information and training are part of the employer's preventive obligations under Art. L.4121-1 and L.4121-2 Code du travail.
In practice, the employer should clearly indicate when work should be stopped, to whom to report feeling unwell, where the first aid station is located and who is responsible on site.
Isolated workers, posted workers, temporary workers and people who do not know local procedures well require special attention. For them, general information alone may not be enough — it is necessary to ensure that the instructions are understood and are applied on the job.
Météo-France alerts and prefectural decisions
The intense heat episode is linked to the Météo-France alert system. This follows from Art. R.4463-1 Code du travail and from the regulation of May 27, 2025, which specifies vigilance thresholds for the system „canicule”.
Therefore, the employer should monitor weather alerts regularly. However, the Météo-France alert alone is not always sufficient to fully assess the situation. In many regions, prefectures may introduce additional, local organizational measures, especially during a red heat alert.
For example, the prefecture may exceptionally allow companies in the construction and public works sectors to start certain works early, for example from 5:00 a.m., to limit workers' exposure to the highest temperatures. At the same time, it may impose an obligation to reduce noise, inform residents and limit nuisances to a strict minimum.
In some cases, it is also possible to temporarily suspend work performed outdoors during the hottest hours of the day if conditions pose a particular risk to the health and safety of workers.
For this reason, during a heat wave, the employer should check not only weather reports, but also the decisions of the relevant prefecture for the department where the work is carried out.
Posted workers and subcontractors
For posted workers, subcontractors and temporary workers, coordination is crucial. The employer, principal, construction manager or health and safety coordinator should ensure that everyone present at the workplace is familiar with the rules in force during hot weather.
This applies in particular to access to water, rest areas, working hours, alarm procedures, the on-site contact person and possible prefectural decisions.
The lack of clear communication may mean that preventive measures formally exist but are not effectively applied by all workers present on the construction site or in the plant.
Practical checklist for the employer
Before and during a heatwave, the employer should check whether:
- the risk associated with high temperatures has been assessed;
- preventive measures have been included in the work organisation and, if necessary, in the DUERP;
- sufficient fresh drinking water was provided;
- employees have access to shaded or cooler rest areas;
- working hours have been adapted to weather conditions;
- the most demanding tasks are not performed during the hottest hours;
- employees were informed about symptoms of overheating;
- team managers know how to react in the event of an employee feeling unwell;
- personal protective equipment is appropriate for working conditions;
- Météo-France alerts and announcements from the relevant prefecture were checked;
- subcontractors and posted workers were given clear instructions.
Summary
A heatwave at work is not just an organizational issue, but a real occupational risk. French legislation requires the employer to assess this risk, implement preventive measures and adapt work organisation to weather conditions.
The most important actions are risk prediction, water provision, adjustment of working hours, exposure reduction, employee information and ongoing monitoring of the situation. In sectors such as construction, public works, agriculture or seasonal work, it is also particularly important to check the local decisions of the prefecture.
A well-prepared procedure allows not only to meet legal obligations, but above all to reduce the risk of accidents, dehydration, heat exhaustion and heat stroke.
