First, we can define a high-death tornado and examine how that definition changes with time. For direct comparison to the 3 May 1999 tornado, we could first consider the frequency of tornadoes associated with at least 36 deaths. Recall that the Oklahoma City tornado was the first tornado in over 20 years to have such a large death toll. In the 1920s and 1930s, 20 such tornadoes occurred. What was once an annual occurrence had not occurred for 20 years prior to 3 May 1999.