I opened the weather app while sitting in the car—86°F, sunny, zero percent chance of rain—so I decided to walk to the coffee shop three blocks away instead of driving. Halfway there, my phone buzzed with a notification from the same app: "Heavy rain alert in your area." I stood there drenched, staring at the little sun icon still cheerfully displayed on my screen, when I realized it had taken actual precipitation falling on my face for the algorithm to update. The app wasn't predicting weather; it was just really good at taking attendance.