Summer’s here and the time is right for stiflingly hot commutes. We’re all familiar with the way the tube becomes a deep-level sauna in the warmer months. But which line is the hottest of all?

Thanks to a canny FOI request by the Gizmodo website, we’ve finally got an official answer from TfL. It’s the baking hot Bakerloo, with an average temperature of 27C in 2016, and a maximum in August of 31C. (Bring on those air-conditioned trains.) Our map shows the other lines you might want to avoid this summer if you don’t want to arrive at work looking like you’ve cycled Mont Ventoux.

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