Anybody who has travelled on the Tube (as we Londoners call the London Underground) knows that in warm weather, some lines are so hot that they make you yearn for Dante’s ninth circle of hell, and the answer to the question “Is the Tube air-conditioned?” is somewhat obvious.
But let’s dive in a bit deeper.
At a glance...
Is the tube air-conditioned?
Well, some tube lines are, some tube lines aren’t.
The Circle, District, Hammersmith & City, and Metropolitans lines all run air-conditioned trains.
And, while we’re at it, the Elizabeth line (technically not a Tube line, but that doesn’t really matter here) is also air-conditioned, as is the Overground (although speaking from personal experience, air conditioning on the Overground seem a bit hit-and-miss), and the newer Croydon trams (also somewhat hit-and-miss, again in my experience).
The remaining lines (Victoria, Piccadilly, Bakerloo, Central, Jubilee, and Waterloo and City lines) are very much not air-conditioned. In fact, on the warmest days, several lines are over the legal limit set by the government for transporting livestock (which is 30ºC/ 86ºF).
And the DLR is not air-conditioned, but it’s not too bad. (Psst… New to London and confused about the different ways to get around? This guide might help.)
So all in all, air-conditioned trains currently run on 40% of the Underground network. Well, it could be worse, I suppose.
This percentage will increase with the introduction of new trains for the Piccadilly line. Amongst other improvements, these will be air-conditioned – yay! This is scheduled to happen some time in 2025. One can hope that in due time, similar improvements can be slowly rolled out to the ovens on wheels carriages on the remaining lines.
So why are some lines air-conditioned, and not the whole network?
Well, in the case of the Circle, District, Hammersmith & City and Metropolitan lines, it’s because they form the subsurface lines, where both the tunnels and the stations are built closer to the surface (between 5 and 15 meters deep). This made it easier to build wider tunnels. Those wider tunnels allow for easier installation of air cooling equipment, and there’s space around the trains where the expelled air can go.
By contrast, the other lines run much deeper (between 20 and more than 50 meters underground), in tunnels that are narrower and not much larger than the trains, so the hot air would not have anywhere to go.
So how hot does the Tube get?
As mentioned above, on those lines without air conditioning, temperatures can climb above 30ºC/ 86ºF. Remember the 2018 heatwave? Temperatures of 35.7 °C (96.26 ºF) were recorded on the Central line, and the Victoria and Bakerloo line weren’t far behind.
And during the 2006 heatwave, temperatures of 47ºC (117ºF) were recorded inside the tunnels. That’s an average summer day temperature in the Sahara!
Which is the hottest tube line?
The Victoria, Central and Bakerloo lines are undoubtedly the hottest, with temperatures constantly reaching above 30ºC/ 86ºF, but the remaining non-air-conditioned lines are not far behind, as evidenced by this chart in the Evening Standard.
Having said that, in 2023, the hottest line was without a shadow of a doubt the Victoria line. Temperatures didn’t drop below 25ºC/ 77ºF all year, with June to October climbing to above 30ºC/ 86ºF. (Source: London data Store)
Does the Tube get any fresh air?
Yes, the Tube gets a supply of fresh air, mainly through the constant opening of carriage doors. In the deeper stations, fans and ventilation shafts help to bring fresh air into the tunnels, and ventilation shafts also help with taking warm air out.
There’s no official list of all the ventilation shafts for the whole system, and TfL will not release such a list on the grounds of “national security and public safety” (fair enough, I guess), but there’s an Open Street Map called “London Underground Vent Shafts”, if you’d like to go hunt for them.
The trains themselves are also ventilated via air vents, sometimes located under the window behind the seats. You know, where people discard their free newspaper after they’ve read it, thereby blocking the flow of fresh(ish) air… Also, in the summer, the windows between the carriages are always open, and the flow of air is very noticeable (and very welcome).
But why is it so hot on the Tube?
And why is it hotter in the deeper sections? One would expect deeper tunnels to be cooler, due to their distance from the surface and potential insulation by the surrounding earth, surely?
The reason this is not the case is that a lot of London is built on clay, and the clay that surrounds the tunnels of the Underground acts as a heat sink. Over the years, the clay has absorbed a lot of heat, raising its temperature. In the early days of the Underground, the clay temperature was around 14°C (57°F), nice and cool. Now, the clay temperature has risen to between 19–26 °C (66–79°F).
Deeper tunnels also mean more limited ventilation, because of the logistics of building deeper ventilation shafts. So the heat generated from the running of trains has fewer opportunities to escape.
How do you stay cool on the tube?
Cool on the Tube is probably too much to ask, but the following might help, especially during a heatwave (or when taking the Victoria line):
As the numerous posters on the Underground say… carry a bottle of water with you. If you’re in a position to freeze the water overnight, so much the better.
Don’t board the first or last carriage, if possible. The closer you are to the middle of the train, the more airflow there will be.
Stay near one of the windows at the carriage ends if you can.
Carry a water spray or facial mist.
Carry a fan. Some of them even come with a built-in water spray.
If you’re able to avoid travelling on the hottest lines, that will help a lot. (I know… duh!)
There you go, I think I’ve covered everything one might want to know about air conditioning on the Tube. Have any more tips? Let me know!
Where to go from there
If you’re looking for things to do and places to eat on any of the tube lines that are air-conditioned, here are some suggestions, the tube/train stops that you’ll need, and which lines they’re on. Click on the link for more information, including detailed instructions on how to get there.
Explore Westminster (St James Park and Westminster – Circle line), and make sure you take in the lovely Lord North Street!
Visit the Museum of St John (Farringdon – Circle line or Elizabeth Line), or the Museum of the Home (Hoxton – Overground), or Sutton House (Hackney Central – Overground) or take in a show at Wilton’s Music Hall (Shadwell – DLR)
- Enjoy the delightful gardens of Inner and Middle temple (Temple – Circle line)
Or how about visiting Ruskin park (Denmark Hill – BR or Overground) or Morden Hall park (Phipps Bridge tram stop)?
And off the beaten track, why not explore the fascinating Trinity Buoy Wharf (East India – DLR)
If you prefer shopping, take your pick from Crofton Books (Brockley – Overgound), the Conran Shop (Sloane square – Circle line), Eclectica (Wandsworth Road – BR) or Rough Trade East (Aldgate – Circle Line, or Aldgate East – District or Metropolitan Line, or Shoreditch High Street – Overground), or why not visit Japan House (High Street Kensington – Circle Line)
Stay cool!
