A second illustration of this is the return period of any
particular value of the number of deaths in a single tornado. By return
period, we mean the time between two events of the same magnitude. As an
example, we have calculated how many days there were between two days with
at least one 10-death tornado on them since 1875 as a function of time.
There are a total of 259 days with at least one 10-death tornado in that
time period. Prior to 1958, return periods of less than 10 days were common.
Since then, the fewest days between 10-death tornado days has been 19
(between the Hall County, Georgia, 12-fatality tornado on 20 March 1998 and
the Birmingham, Alabama, 32-fatality tornado on 8 April 1998).