On April 3rd - April 4th in 1974 a total of 148 tornadoes struck thirteen states killing 315, injuring 5300 and causing 600 million in damage all in a span of just sixteen hours. Cold air from the north was moving south as warm, moist air moved north from the Gulf of Mexico. The jet stream was also playing a role with speeds over 140 mph. The clash of the warm and cold air coupled with the strong jet stream which added the wind shear component created an environment perfect for a massive outbreak. A tornadic thunderstorm developed near Decatur, Illinois beginning the 'super outbreak'. The F5 that hit Xenia, Ohio left 34 dead and half of the town in destruction. The top winds in Xenia were estimated at an incredible 318 mph ! Alabama, Georgia, Illinois, Indiana, Kentucky, Michigan, Mississippi, North Carolina, Ohio, South Carolina, Tennessee, Virginia, and West Virginia were all the states affected. Six of the tornadoes were F5. Winds were in excess of 261 mph.
April tornadoes are the strongest due to the greatest temperature contrast both horizontally and vertically. May is usually the most prolific month with eighteen percent of the annual average. Seventy five percent of all tornadoes occur between March and July. For the Metro Area the months of July through September are our critical months. Virginia averages six tornadoes per year while Maryland averages five. There have been six known tornadoes in the District. The La Plate tornado was an F4 and the second strongest tornado to hit the east coast with winds up to 200 mph.