Pinging weather stations should be a good indicator. If you notice a bunch of contiguous ones no longer responding, or sending back huge temperature readings, there's a good chance a nuclear apocalypse is imminent. (Just ignore the few statistical outliers: https://www.cnn.com/2026/04/23/europe/france-weather-sensor-...)

> there's a good chance a nuclear apocalypse is imminent.

Or that an excavator took out some fiber.