The Finnish mobile phone giant, Nokia, has proposed a warning system that senses the radio waves produced by bolts of lightning.

Each bolt produces frequencies between 10 hertz and 5 gigahertz, and the distribution of these signals depends on how far away the lightning is.

The multiple receivers in a phone, such as Bluetooth, FM, tri-band GSM, Wi-Fi and RFID, can be tuned to pick up these signals, says Nokia (US patent application 2007/0085525).

Software will then interpret them, work out the distance to the lightning, and tell you if strikes are getting closer.

From New Scientist magazine