When rain pours for 24 hours straight; like it did in Mumbai, Delhi, and Bengaluru recently; the real danger quietly begins underground. Sewage overflows. Water tanks become mosquito nurseries. Rats flee flooded sewers... and bring diseases like leptospirosis into homes. A 2025 study warns heatwaves will double in major cities by 2030, and rainfall events will rise 43%. That’s not just weather; it’s a disease accelerator. Doctors like Surya Prasad in Bengaluru are already seeing cholera, hepatitis E, and dengue pop up outside their usual seasons. Infrastructure built for yesterday’s climate is failing today’s reality. Storm drains designed for 25mm/hour rain are drowning under 100mm storms. In Kolkata and Mumbai, some underground pipes are over 100 years old; and no one even has updated maps of them. Climate isn’t just changing temperatures; it’s rewriting how, when, and where we get sick. The next outbreak might not come from a distant country. It could come from your own tap.