A few significant Plains tornado events during April
1938 Oshkosh, Nebraska tornado outbreak, April 26, 1938.
April 1939 tornado outbreak sequence, April 14-17, 1939.
April-May 1942 tornado outbreak sequence, April 27-30 & May 2, 1942.
April 1945 tornado outbreak, April 12, 1945.
1947 Glazier-Higgins-Woodward tornadoes, April 9-10, 1947.
Early-April 1957 tornado outbreak sequence, April 2, 1957.
1957 Lubbock tornado outbreak, April 21, 1957.
1964 Wichita Falls Tornado, April 3, 1964.
April 1970 Tornado Outbreak, April 17-18, 1970.
1979 Red River Valley tornado outbreak April 10-11,1979
April 1980 Central United States tornado outbreak, April 7-8, 1980
1984 Morris, Oklahoma tornado outbreak, April 26-27, 1984.
1984 Mannford-New Prue, Oklahoma tornado outbreak, April 29, 1984.
April 26, 1991 tornado outbreak April 26-27, 1991.
1993 Catoosa, Oklahoma tornado outbreak, April 24, 1993.
April 1994 tornado outbreak, April 25-27, 1994.
April 10-11, 2001 tornado outbreak, April 10-11, 2001.
Easter Week 2006 tornado outbreak sequence, April 13-19, 2006.
April 20-26, 2007 tornado outbreak sequence, April 20-27, 2007.
April 2009 tornado outbreak, April 9-10, 2009.
April 9-11, 2011 - Iowa, Wisconsin, Texas, Missouri, Alabama - 2011 Iowa-Wisconsin tornado outbreak.
April 3, 2012 - Texas, Louisiana, April 3, 2012 tornado outbreak.
Notable April Tornadoes in Texas
THE ROCKSPRINGS TORNADO - APRIL 12, 1927
The third deadliest tornado in Texas history, like the first and second, occurred well south of what is generally considered Tornado Alley. This F5 tornado touched down 3 miles to the northwest of Rocksprings, in Edwards County, and moved toward the southeast. Nearly 1 mile wide as it crossed Rocksprings, it destroyed 235 of the 247 buildings in the town. It killed 74 people and injured 205, almost 1/3 of the population. Clearing Rocksprings, it continued southeastward at least 35 miles and perhaps as far as 65 miles.
THE GLAZIER-HIGGINS-WOODWARD TORNADOES - APRIL 09, 1947
The fourth deadliest tornado in Texas history also moved through western Oklahoma and dissipated near St. Leo, Kansas. Part of a family of deadly twisters, it touched down 5 miles northwest of Pampa and crossed just northwest of Canadian, nearly parallel to US 60. It's funnel was reported at times to be between 1 and 2 miles wide. Just before crossing into Oklahoma, it destroyed the town of Glazier and most of the town of Higgins. It killed 17 and injured 40 in Glazier and 51 persons were killed, 232 injured in Higgins. Final totals across three states were 181 killed and 970 injured.
THE WICHITA FALLS TORNADO - APRIL 10, 1979
One of the most infamous of Texas Tornadoes, this huge F4 first touched down about 3 miles northeast of Holliday, a town lying southwest of Wichita Falls, where it damaged homes and businesses. Crossing into Wichita Falls, it severely damaged Memorial Stadium, followed by Mc Neil Junior High, and then entered the residential part of the city. It damaged a shopping center and numerous vehicles, then proceeded across US 287 where it destroyed additional vehicles. At times it was a mile and a 1/2 wide. It continued northeast from Wichita Falls, past the Red River and into Oklahoma where it dissipated north of Waurika. It killed 42 people in Wichita Falls, 25 of those deaths were vehicle related. It caused over 1700 injuries, destroyed over 3000 homes and left 20,000 homeless.
This article discusses the significance of April as a severe weather maker:
April Showers Bring May Flowers and Severe Weather by Kathryn Prociv, Washington Post