Carriages in three London Underground lines are expected to heat up to over 30°C this summer, with the hottest forecast to hit 32°C, new figures suggest.
Only 40% of trains across the network have air conditioning – on the Circle, Hammersmith & City, District and Metropolitan lines – keeping temperatures around 19.3°C on average.
On older lines, Transport for London (TfL) says it has fitted cooling systems in stations including ‘industrial-sized fans and chiller units’.
But the trains themselves are prone to get uncomfortably hot in heatwaves like the one whick kicked this week off.
This summer’s hottest lines have been forecast by Making Moves, based on past temperature data obtained through Freedom of Information requests, and ranked.
Which tube lines are set to be the hottest?
The Victoria Line tops the list, as it’s expected to hit 32°C at the peak of the heatwave.
If this happens, it would be the hottest temperature ever recorded on a Tube line.
It has recorded the hottest average temperature every year since 2021.
Last year average hottest daily temperatures on the line came in at 28.1°C – more than twice the average outdoor temperature.
The highest historical temperature ever recorded on the line was 31.25°C in September 2023.
These are the seven lines with the highest peak temperature forecast for this summer:
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The Victoria line hasn’t always been the hottest: from 2013 to 2020, the Bakerloo line held onto the crown.
It’s responsible for the hottest Tube temperature on record, hitting 31.75°C in August 2019.
Forecasts for The Circle, District, Hammersmith and City, DLR, Elizabeth, Metropolitan, London Trams, IFS Cloud Cable Car and all London Overground Lines were not included in the research, as data was not available.
All Tube lines on that list (as well as the London Overground) have air conditioning, so they wouldn’t show up on a rankiing of hottest lines.
But Making Moves also forecast the minimum 2025 average temperature for most Tube lines.
Due to the missing contenders, the ranking doesn’t say much about where passengers can expect to keep coolest.
But those wanting to avoid hot carriages may be interested to note which lines fail to cool below temperatures which many may find uncomfortable.
Here the seven lines ranked by minimum predicted temperature:
- Waterloo & City – 17.5°C
- Picadilly – 20.3°C
- Northern – 22.6°C
- Bakerloo – 22.9°C
- Central – 23.2°C
- Victoria – 25.4°C
- Jubilee – 26.2°C
Despite these temperatures, TfL has only received 134 formal complaints about excessive heat on the Tube over the past three years.
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