Cramped into the Piccadilly line is the last place you want to be during a heatwave. But that wasn't always the case...
"The coolest resort in London, with the exception of the refrigerator, was in the underground subway of tube stations," reckoned the Daily Mirror during an unseasonable hot spell in May 1916.
The temperature inside a "stuffy West End shop" was 31.7°C, while one of the deep-level Tube lines was just 23.9°C (or 89°F versus 75°F in ye olde units of the report).
So, a heatwave day in May 1916 saw the Tube hit almost 24°C. According to London Datastore numbers, an *average* May day on the deep-level lines today is 26.6°C (Bakerloo) or 27.5°C (Central). These can easily exceed 30°C during a heatwave.
Another news item from 1914 recorded the subsurface temperatures on the Metropolitan line.
