A new study in *Nature Cities* reveals that subway riders in New York, Boston, and London are increasingly using social media to complain about rising temperatures in subway systems. Researchers at Northwestern University analyzed over 85,000 social media posts and Google Maps reviews from 2008 to 2024, focusing on keywords related to 'thermal discomfort.' The study found that a 1-degree Fahrenheit (0.56-degree Celsius) increase in outdoor temperature led to a significant rise in complaints: 10% in Boston, 12% in New York, and 27% in London. This trend is expected to worsen as climate change continues to elevate global temperatures.