Need details about a past severe weather event in your county? Maybe you're just trying to settle a bet about when an event actually occurred. Or maybe you need information on major storms because you're planning to build a conservation structure and want to check how expected life stands up against real-world storm data.
Whatever the reason you have, Ken Scheeringa says the federal agency that archives weather data has an online data base that lists all significant storm events for the U.S. since 1950.

First, go to the Storm Events website, powered by NOAA. Select your state, then select the "search" button. On the next page, choose your beginning and ending dates to search, your county and type of event of interest. To search the entire state, set county to ALL. To search for all types of events, set event type to ALL.
Click the search button again to find your results. If underlined links show in the 'location output' column, click them to bring up detailed notes written about the event.
Need a practice run? Set state to Indiana, start and end dates to 4/3/1974 and event to tornado. Then hit search. If you do that, the search engine will bring up 54 events – 54 tornadoes, on that one day. The report lists individual counties where tornadoes were verified, including the strength rating of the tornado. It also gives number of fatalities and number of injuries. Forty-seven Hoosiers were killed in that outbreak and more than 800 more were injured. All the data accessed from the site is the official data weather sources file and keep after investigating any type of storm event. It's not based on witness reports during the event.
Why doesn't the database include weather events for the most recent months? It's because preliminary data is still being edited. You can find them in another location.