brontometer

from The Century Dictionary.

• noun An instrument devised by G. W. Symons, and constructed in 1888, for registering simultaneously the time of beginning and ending of lightning, thunder, rain, wind, and other phenomena of thunderstorms. More properly a brontograph.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Meteor.) An instrument for noting or recording phenomena attendant on thunderstorms.