The local NWS offices initially gather the data, starting when a severe weather event unfolds and continuing until sufficient information is obtained.

Original sources of the data include but are not limited to local law enforcement, local, state, and federal emergency management, storm spotter and storm chaser reports, the news media, insurance industry data, NWS damage surveys, and reports from the general public.

Another is the DAPPL (short for Damage Area Per Path Length) database that was headed by Ted Fujita at the University of Chicago and concerns the period from 1916 to 1992.

Storm Data publishes chronological tabulations, narratives, and images for a calendar month, as well as updates to previous publications.

Type of occurrence, location (including municipality and county as well as estimated latitude and longitude), date and time, magnitude of event (i.e. wind speed, Fujita scale rating, Saffir-Simpson Hurricane Scale rating, hail size, storm surge or river crest height, etc.

[2] For fatalities, demographic information such as age and sex are gathered when possible as is the type of location (frame house, mobile home, apartment, outside, vehicle, church, school or other public building, etc.)