Tornadoes in the U.S. typically increase sharply in spring. Unfortunately, a few of those can be violent tornadoes, particularly in the South. On March 3, 1966, 59 years ago today, an F5 tornado ...

But the biggest difference ... for various types of buildings and structures. As a result, tornadoes that might have been classified as F5 under the old system could now be assigned an EF4 ...

A quirky aspect of the way we measure twisters helps explain why there hasn't been a top-tier-rated tornado in 12 years.

The most tornadoes reported in a single year was 258 in 2015, including the largest outbreak in Central ... Violent tornadoes — those rated F4/EF4 and F5/EF5 — are much rarer.