If you're struggling in the heat today, spare a thought to poor old Londoners, many of whom will have to venture deep underground. Yes, this might sound and look like madness to any outside observers, but this is how things are done in the capital.
According to the Independent, temperatures could reach as high as 33 degrees underground - which is more than the legally allowed limit for livestock. (Most livestock transport guidelines say that animals must be able to turn around too - but let's not get too ambitious.)
So what can be done? Here's some top tips on how to stay cool on the tube:
Optimise Your Journey For Speed
If you want to master London's public transport, then make sure you've got CityMapper downloaded on your phone. The app is perhaps even smarter than Google Maps, as it takes all of the real-time data provided by Transport for London and will mash it up to figure out how to get you from A to B in the quickest time possible.
There's not just tube data (it will even tell you how long before a train is coming), but live bus data too. You can even have it figure out how much an Uber to your destination would cost.
Walk Between Stations
It is often surprising to non-Londoners, but it is actually quicker to walk between many tube stations. For example, Euston is only a short walk from Kings Cross St Pancras, and Lancaster Gate isn't a million miles away Paddington. There's plenty of examples like this, and you can find an unofficial map here.
More broadly, it is important to remember that the Harry Beck tube map we all know and love massively distorts London's geography - so if you have a bit of flexibility in your schedule, it can be more pleasant to walk through central London. It'll only take about half an hour to walk from Euston Road (where the stations on the top of the Circle Line are) down to the river, for example. You can find a full map of walking distances here.
Get to the Exit Quickly
When it is super hot, you want to be in and out of the Underground in the quickest time possible - no messing about traipsing around the platform looking for the right way to go. So before you head underground, download the app Tube Exits, which works as an offline database of the best places to stand on the platform to be closest to the exit at your destination.
Station Master offers similar functionality too - as well as a host of other useful functions, such as entire 3D maps of tube stations so you can pre-visualise exactly where you need to go.
Stick to the Sub-Surface Lines or the Overground
After what must have been decades of commuters moaning at TfL, the first tube trains with air conditioning were introduced in 2010. The "S-Stock" is now running on the sub-surface tube lines: The Circle, District, Metropolitan and Hammersmith & City lines. So take one of these lines and things might be significantly cooler than the deeper lines.
The London Overground similarly has recently upgraded to modern British Rail Class 378 trains which have on-board air conditioning.
Sadly, if you're hoping for cooler trains on the other lines you could be in for a long wait. Due to the smaller tunnels and challenges of ventilating warm air, getting AC on the Central, Piccadilly, Bakerloo and Victoria lines isn't going to be happening any time soon.
Avoid the Central Line
Seriously. TfL actually monitor the average temperatures on different parts of the Tube, and according to this analysis by CityMetric, the Central Line is the hottest - followed by the Bakerloo, Piccadilly, and Northern.
Avoid Rush Hour
Less people, less problems. So try to avoid travelling when everyone else does. According to this TfL report, those times are exactly when you might expect: Between 7 and 9am, and between 4 and 7pm, as everyone trudges back to the suburbs.
The Economist has an even more detailed chart showing demand here.
Bonus Tip: Avoid the "Roastmaster" Routemaster Bus
Okay, it isn't the Tube, but you might want to avoid taking the bus too, especially if it is one of Boris Johnson's "New Routemaster" vanity buses. Yes, they look cool but inside they are anything but, as the design doesn't allow for windows that can be opened. The air condition is terrible too - which is why they've earned themselves the nickname "The Roastmaster".
Here's the bus routes to avoid:
8 - Oxford Circus to Bow Church
9 - Hammersmith to Aldwych
10 - Hammersmith bus station to King's Cross St. Pancras
11 - Liverpool Street station to Fulham Broadway
24 - Hampstead Heath to Pimlico
38 - Victoria to Hackney
55 - Oxford Circus to Leyton
137 - Oxford Circus to Streatham Hill
148 - Camberwell Green to White City bus station
390 - Notting Hill Gate to Archway
453 - Marylebone station to Deptford Bridge
One mischievous Londoner once got Emma Hignett, the familiar voice that announces bus stops, to record the following at a special event to promote TfL's bus heritage...
Carry a Bottle of Water
Look, I don't want to sound like your mum, but you should carry a bottle of water and stay hydrated. Trust me, you'll thank me later.
Don't Wear Trousers
The American group Improv Everwhere have for a number of years, in a brazen example of diminishing returns, held an annual "no pants" subway ride. Which is exactly what it sounds like, albeit without the dirty connotations your mind is now drifting towards.
What they've realised that if just one person does it, they will probably get in trouble - but if loads of people do it, then suddenly it becomes socially acceptable. So when you're heading home on the Tube this evening, why not announce to the carriage that you want to take your trousers off, inviting the rest of the carriage to join you? It just might work.
Screw work, go to a pub with a beer garden
Come on. It's summer. It's lovely outside. That's basically authorisation to skive off and spend the day in the pub, right? TimeOut London has a list of some pubs in the capital with beer gardens - so why not head to one of these instead of crowding on to an unbearable train?