As we near the end of the 1990s, tornado activity has again shown an increase. This trend is worth further study to determine causes of the decadal tornado cycle. While at least one tornado has occurred in the Tulsa CWA each year since 1950, the decadal cycle should lead to more conscientious preparedness efforts during the early and latter years of a decade. Yearly Distribution of Tornado Reports. Summary Large hail is the most common type of severe weather, followed closely by severe wind.
Tornadoes come in a distant third.
April, May and June are the most active severe weather months of the year. There is a small secondary peak in October and November. The winter months are the least active. Late afternoon and evening are the most active times of day for severe weather. Violent F4 and F5 tornadoes account for a disproportionately high number of tornado-related deaths and injuries.