Heat waves, snowstorms, and torrential rains are already altering travelers’ behavior and putting pressure on urban and suburban public transportation. A study conducted in Île-de-France, the Paris metropolitan area, shows that extreme weather events alter travel decisions, reduce the use of certain modes of transport, and increase passengers’ expectations regarding real-time information, sheltered spaces, and service adaptation.
The analysis, published by L’Institut Paris Region in collaboration with Mass Transit Academy, Transilien SNCF Voyageurs, DRIEAT, CCI Paris Île-de-France, and Sustainable Mobilities, is based on a reality relevant to all major metropolitan areas: transportation infrastructure must operate in an increasingly unstable climate.
In the Paris region, the stakes are high. The region has 12.5 million residents, over 41 million daily trips—more than 9 million of which are by public transit—and is exposed to both urban heat island effects and the risk of flooding from surface runoff. Between September 2022 and February 2026, the study identified 176 days with exceptional weather conditions, including extreme heat, freezing temperatures, snowfall, high winds, or heavy rain.
The Paris Region: A Case Study in Mobility Under Climate Pressure
The study analyzes how weather influences the use of different modes of transportation, from trains, RER, and the metro to buses, trams, bicycles, and cars. The conclusion is that the impact of extreme weather is not uniform: some modes are heavily affected, while others prove more resilient.
Bicycles are the mode of transport most sensitive to weather conditions. On weekdays, bicycle use in Paris drops by 18% at 0°C compared to a day with an average annual temperature of 14°C, and on weekends the decline reaches 41%, a sign that leisure trips are easier to cancel than essential ones.
In contrast,the metro is very little affected by the weather, as it is mostly underground. The analysis did not identify a significant impact of temperature or precipitation on metro use.
For the RER and trains, the effects are moderate but noticeable. On weekdays with high temperatures, RER and train use drops by approximately 4% compared to a day with average temperatures. The percentage seems small, but in Île-de-France it means nearly 150,000 fewer trips on a weekday—a volume greater than the total traffic on Line N.
Rain increases traffic congestion
Heavy rain affects each mode of transport differently. On workdays with precipitation exceeding 5 mm, bicycle use drops by 24% compared to dry days. Bus and tram use declines by approximately 4%, while RER and train use falls by 2%.
For road transport, the picture is more complicated. Traffic on the main network decreases slightly, by 3%, but congestion increases by 31%, likely due to reduced visibility, lower speeds, greater safety distances, and the rapid risk of network saturation.
The study thus shows that, under difficult weather conditions, a decrease in the number of trips does not necessarily mean smoother traffic flow. In the case of roads, rain can reduce traffic but can make the network more vulnerable to gridlock.
Snow remains the most disruptive phenomenon
Although snowfall events may become rarer in the context of climate change, the study shows that snow remains the weather phenomenon with the strongest impact on mobility.
In a survey conducted by Ipsos BVA for Transilien SNCF Voyageurs, 72% of respondents cited snow as one of the most disruptive weather phenomena for travel. Additionally, 46% of those surveyed said that, in the event of snowfall, one of the first measures taken is to cancel their trip.
Companies confirm the same impact. In a survey conducted by the CCI Paris Île-de-France, 95% of firms cited snow and ice as the phenomena that most affect employees’ ability to get to work, leading to delays and widespread absenteeism.
However, public transit holds up better than road travel. During the snowstorm on January 7, 2026, when authorities called for a strict limit on travel, ridership dropped by 31% for the RER and trains and by 11% for the metro, while road traffic fell by 50%.
Heat waves are becoming an increasingly frequent problem
While snow is the most spectacular disruptive phenomenon, heat waves are the risk that will become increasingly common. In Île-de-France, the number of days with extreme heat could rise from 7 per year currently to 19 in 2050. At the same time, the number of days with very heavy rain could increase by 30%, while snowfall events are expected to decrease.
During heat waves, the impact on transportation use is less significant than during winter events, but it remains clear. Buses are the most affected, with declines of between 8% and 20%, followed by the RER and trains, where the drop could reach 12%. Road traffic could decrease by up to 8%.
For passengers, heat waves are felt not only as a mobility issue, but also as one of physical and psychological comfort. Public transportation becomes an uncomfortable space when vehicles are not air-conditioned or when crowding is high.
The study also notes a significant difference in perception. Passengers understand the effects of snow on the rail network more easily than the effects of a heatwave.
However, high temperatures may require speed limits in certain areas to reduce risks related to rail warping or overhead wire issues.
Nearly half of the region’s residents consider a 30-minute trip delay acceptable in the event of snowfall, but less than a quarter accept the same in the event of a heatwave.
Remote work reduces pressure on the network
One of the study’s most important findings is the role of remote work as an adaptation tool. According to the Ipsos BVA survey, 46% of employees in Île-de-France regularly work remotely. If we include those who work exclusively remotely or have the option to do so without regularly teleworking, the proportion rises to 63%.
During heat waves, two-thirds of those who can work from home prefer to stay at home. The main reasons are to avoid the heat during the commute and the fact that the temperature at home is more bearable than at work.
But the study also highlights a significant social vulnerability. 27% of employees in Île-de-France cannot work remotely and have no flexible hours, and two-thirds of them are women. In addition, some employees unable to work from home do not own a car and rely on public transportation.
For this group, extreme weather events cause high stress, fatigue, and a sense of unfairness. One-third of employees in the blue-collar and white-collar categories have already lost part of their salary or a day of vacation due to difficulties commuting to work during extreme weather events.
Commuters do not easily switch modes of transportation
The study shows that modal shift is still rarely used as an adaptation strategy. When faced with extreme weather events, travelers prefer to reduce their trips or reschedule them.
On average, 35% of respondents cite reducing trips as one of the main measures taken, while 33% choose to reschedule them. Only 15% cite changing their mode of transportation as the primary solution.
The study’s authors believe that more education is needed to promote multimodality, especially among those who regularly use cars. In the event of extreme weather, the mere existence of an alternative is not enough if users are unaware of it, do not trust it, or do not perceive it as practical.
Real-time information and sheltered waiting areas
Passengers’ expectations are clear. 67% of respondents want better real-time communication regarding train schedules, and 55% request clearer information about available alternatives in the event of service disruptions on a line.
Additionally, 60% of travelers are calling for the installation of sheltered waiting areas to protect them from rain, wind, or sun. This expectation is even stronger among women, being mentioned by 66% of female respondents.
Companies, for their part, are calling for the continued installation of air conditioning in rolling stock, improved reliability and frequency of passenger information, better service between suburbs, and the maintenance of bus service in the event of disruptions.
The study also suggests integrating weather information into transportation apps, including Météo-France alerts and travel recommendations from authorities. Conversely, weather apps could include mobility recommendations.
Lessons from COVID and Paris 2024
The study’s authors argue that the experience gained during the pandemic and the Paris 2024 Olympic and Paralympic Games can be used to manage mobility under extreme weather conditions. Measures that reduce or redistribute transportation demand over time and space—already used in crises or major events—could be adapted for heat waves, snowstorms, or heavy rain.
The idea is for operators, authorities, companies, and travelers to participate in a more flexible mode of operation for the transportation system, adapted to extreme conditions.
In the long term, the region will need investments in infrastructure resilience. In the short term, however, the study shows that better information, telework, flexible schedules, and clear communication regarding technical difficulties on the network can reduce the pressure on public transportation.
As extreme weather events become more frequent, public transportation will need to be not only more technically resilient but also better adapted to the actual behaviors and needs of passengers.
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