There is this ultrasonic-windsensor which will be mounted on a bridge in winter. Maybe several of them.

In the manual it strictly mentions the following:

It seems like for outdoor use this device should be earth grounded(probably through mains earth? since no earth on bridge). In the manual the reason is given as radio freq. interference and lightning.

People are asking why would there be RF interference on a bridge in the middle of no where and why would lightning affect this device.

Would a lightning not a direct strike on such device but nearby still affect the performance or damage it?