Heatwave: which metro and RER lines are air-conditioned for a cooler ride?

A vague de chaleur has struck France in recent days, pushing temperatures up to 40°C in places. Under these conditions, journeys on public transport can be unpleasant, especially during rush hour when carriages are crowded. And if these metro, RER, or tram cars aren’t air-conditioned, the trip can feel endless and resemble a near-free sauna—though not necessarily a pleasant one.

To reach your various appointments and traverse the capital, you won’t always be able to choose your routes. But when you can, opt for the most enjoyable ways to get around.

For this period, we've listed the various metro, RER, streetcar and bus lines that are air-conditioned. If you're prepared to make a few detours, here are the lines to choose from this summer.

• To be read
• This week's top picks in Paris and Île-de-France, June 22–28, 2026

RATP distinguishes between three types of ventilation: refrigerated ventilation (air conditioning), forced mechanical ventilation (outside air is drawn in and diffused inside) and natural ventilation (windows open and draughts).

• Air-conditioned lines:
  • In the metro
    Lines 1, 2, 5, 9, 11, 14
  • In the RER
    Around 84% of the RER B and about one-third of the RER C
  • In the tram network
    All tram lines
  • In the bus network
    Nearly 75% of buses should be air-conditioned. Prefer hybrid or electric buses, the newer models.
  
  
• Lines with forced mechanical ventilation:
  • In the metro
    Lines 4, 7, 7bis, 8, 13
  • In the RER
    Some trains on the RER B
  
  
• Lines with natural ventilation:
  • In the metro
  • Lines 3, 3bis, 6, 10 and 12
  • In the RER
  • RER D, RER E
  • In the bus network
  • Vehicle air conditioning is being rolled out, but a significant portion of Île-de-France buses still rely mainly on natural ventilation.

Soon air conditioning on all forms of transport?

Why aren't all public transport lines air-conditioned? On its website, RATP explains that this option has major ecological consequences, and that numerous physical and material constraints prevent the installation of air-conditioning systems.

«The air conditioning of rolling stock running underground is not the chosen solution because it has a heavy environmental footprint, consuming a lot of energy that reappears as heat, which is inevitably pushed back into the tunnels and onto the platforms. Moreover, it is not suited to the regular opening of doors», reads a blog post dated 2018. In a more recent post (dated 2025), the RATP adds: «Thus, while an air-conditioned train offers passenger comfort, it would automatically heat the spaces (stations), the system requiring the expulsion of warm air to the outside.»

However, this state of affairs could change in the coming years. In an interview with Le Parisien, Grégoire de Lasteyrie, Mayor of Palaiseau (DVD) and Vice-Chairman ofÎle-de-France Mobilités, explains: " For years, for ideological reasons, the widespread introduction of 'air conditioning' in Ile-de-France transport systems was not on the agenda. Since 2016, for President Valérie Pécresse and myself, things have become clear: air conditioning is not an option! Because without air conditioning on public transport, people will prefer to take their cars. And it's better to have one air-conditioned bus than 10 individual cars with the air conditioning on full blast."

To breathe and get some fresh air during these hot months, you can also opt for outdoor means of transport: electric scooters, bicycles, rollerblades...