The London Underground can easily top 30 degrees in summer months, but now data has confirmed which line is the officially the hottest
During the most recent heatwave, Transport for London was forced to put in place a comprehensive hot weather plan in the hope of keeping passengers as comfortable as possible.
TfL said air conditioning was in place on some lines and urged passengers to carry water and to “look out for each other while travelling”.
Bosses say 40% of trains across the network have air conditioning, including the Circle, Hammersmith & City, District and Metropolitan lines, which have the coolest temperatures (19.3C) on average.
London Overground and Elizabeth line trains are also conditioned but on older lines, it says it has introduced “a range of station cooling systems including industrial-sized fans and chiller units to pump in cold air”.
Now Making Moves has predict which tube lines will be the hottest and coldest in 2025, to “help you travel smarter, not harder”.
The group submitted a Freedom of Information Request to Transport For London for complaint data relating to the lines being too hot or cold, made between 2022 and March 2025 and then obtained from Transport for London via the London Datastore for individual tube temperature data from 2013 to 2024.
Data science models were then utilised in order to predict which lines will be the hottest and coldest for the remainder of 2025.
Which tube lines will be the hottest this year?
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The Victoria Line has the highest maximum predicted temperature for 2025, and is set to reach a sweltering 32C in the peak of the heatwave. From 2021 to 2024, the Victoria Line has consistently recorded the average hottest temperature, with an average of 28.1C for the entire of 2024 and last year received the most amount of complaints from fed up, hot and bothered commuters.
In 2024, there were 19 official complaints made, followed by 30 in 2023 and 29 in 2022.
Nigel Howard / Evening Standard
Next up for sweaty journeys is the Central Line in second place with the second highest maximum predicted temperature for 2025, likely to peak at 31.4C in August.
Central Line is one of London’s oldest and deepest lines so it’s no surprise that the limited ventilation available contributes to making this line being one of the hottest.
This line ranked second for complaints also.In 2024 it had 9 complaints followed by 3 in 2023 and 7 in 2022.
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The Bakerloo Line at Elephant and Castle station
Southwark Council
The Bakerloo Line is set to see the third highest temperatures for the Underground.
Experts predict maximum temperatures of 30.1C during the summer months in the capital here.
The line has seen four complaints in total since 2022 because of unbearable temperatures.
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Ross Lydall
This line is expected to see a maximum predicted temperature underground of 29.1C in the coming months, leaving the line in fourth place for hot and sweaty journeys.
The line received 15 heat related complaints since 2022, ranking the line higher on complaints than the Bakerloo line, despite being slightly cooler.
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It is still hot on here, but nearly four degrees cooler than the hottest Line.
Piccadilly line is a central serving line, and very well used with experts saying they expect it to get to a maximum temperature of 27.7C soon.
The line has had 8 heat related complaints since the start of 2022 to 2024.
A Jubilee line Underground train in Bond Street station in central London (Jonathan Brady/PA)
PA Archive
This line is set to see a maximum temperature of 26.2C on the hottest days of the year, which experts believe we are yet to see.
A heatwave is expected in the coming days which could see the hot underground temperature hit.
The line has received 10 heat complaints since 2022 – three in 2024, five in 2023 and two in 2022.
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Ross Lydall
The coolest on our list – the Waterloo and City Line, which connects many overground stations, is expected to see maximum temperatures of 25.1C.
This line also tops the table for the coolest as far as complaints go, and has received zero complaints about heat levels over the last four years.