The U.S state of Iowa experiences multiple tornadoes every year. There have been at least 3,502 recorded tornadoes since 1876. At least 6,447 people have been injured, and 933 people have died due to these tornadoes. The deadliest tornado was the Camanche tornado which killed 72 people in Iowa. 
The most tornado-prone parts of Iowa are in the Northeastern counties. The counties of Delaware, Black Hawk, Buchanan, Linn, and Benton on average have seen at least 1 strong tornado each year from 1953 to 2008.
Climatology.
Although tornadoes can happen at any time of the year, the most popular time for tornadoes to form in Iowa is from April through June. Iowa is in the central plains, where the Rocky Mountains to the west and the Appalachian Mountains to the east meet. This unique geography creates a funnelling effect, channelling warm, moist air from the Gulf of Mexico and cool, dry air from Canada. These are the most ideal conditions for tornadoes to form with Iowa being caught inside of tornado alley, along with other great plains states, greatly increasing the chances of a tornado to form in Iowa.
Intense tornadoes.
Pre-1900.
A total of 155 recorded tornadoes touched down in Iowa before 1900. At least 540 people died and 2,186 people were injured due to these tornadoes before 1950. There have been 37 intense tornadoes with a rating of F4+, or 2 or more fatalities, the deadliest of which being on June 3, 1860, in Camanche, killing 92. This time period for tornadoes in Iowa is the deadliest period of tornadoes in Iowa, with each recorded tornado killing on average 3.48 people. The first use of a tornado warning in the United States wasn't until March 25, 1948. This caused tornadoes before the 1950's to be more dangerous because people wouldn't realize a tornado would be headed right towards them.
Camanche Tornado.
On June 3, 1860, an F4 tornado touched down north of Bennett, moving across eastern Iowa, killing 20 people in rural Clinton County. It then ripped through Camanche, destroying almost every building in the town and killing 41. A raft carrying 26 was hit by the tornado and flipped, killing all but 3 men. The tornado had a damage path of 1,000 yds (914,4 m) wide, and 81.2 mi (130,68 km) long.
Grinnell Tornado.
On June 17, 1882, an F5 tornado touched down in Cooper. It travelled across central Iowa, killing a total of 68 people. 10 people died near Rippey, 7 people died in Jasper County, 39 in Grinnell and 10 in Malcolm. The tornado had a damage path of 109.4 mi (176.06 km) long and 800 yds (731.52 m) wide.
Pomeroy Tornado.
On July 6, 1893, an F5 tornado touched down Northwest of Quimby, moving towards the town of Pomeroy. With a damage path 500 yards (460 m) wide and 55 miles (89 km) long, the tornado destroyed about 80% of the homes in Pomeroy. The tornado killed 71 people and injured 200.
1900-1949.
A total of 352 tornadoes touched down in Iowa between 1900 and 1949. At least 292 people died and 1,861 people were injured. There were 43 intense F4+, or 2 or more fatalities, tornadoes, the deadliest of these tornadoes would be the 1913 Easter tornado that hit Omaha, Nebraska, making its way over the border into Iowa, killing a total of 103 people, and injuring 350 others.
Omaha Easter Sunday Tornado.
An F4 tornado touched down in La Vista, Nebraska, a suburb of Omaha, traveling through the city of Omaha and crossing the border into Iowa. In total, 103 people died, 9 of which being in Iowa. The tornado had a damage path of 40.3 mi (64.86 km) long and 400 yds (365.76 m) wide.
Crawford County Tornado.
On May 21, 1918, an F5 tornado touched down in Crawford County, moving across the county and into Greene County as well. According to witnesses, twenty or more farms were destroyed and a couple riding in a buggy north of Churdan got caught by the tornado and died. Mattresses were carried two miles away and farms and homes were wiped completely off their foundations.
1950-present.
A total of 3,117 recorded tornadoes have touched down in Iowa since 1950 causing 101 deaths and injuring 2,400 others. There has been 20 (E)F5 tornadoes, or 2 or more fatalities, the deadliest being the 1968 Hansell-Charles City tornado, killing 13 and injuring 462 others.
1968 Hansell-Charles City tornado.
On May 15, 1968, a multi-vortex tornado hit the communities of Hansell, Hampton, Charles City, Elma and Aredale, all located in the state of Iowa. It killed 13, injured 462, and hundreds of buildings were destroyed, primarily in the town of Charles City. Damage estimates were of more than $20 million. All the deaths occurred in Charles City.
2008 Parkersburg-New Hartford tornado.
On the afternoon of May 25, 2008, as part of a large tornado outbreak across the central plains, a large and extremely powerful EF5 wedge tornado devastated the towns of Parkersburg and New Hartford, Iowa. The tornado killed nine people and caused about $75 million in damages across in its approximately 43 mile path across northeast Iowa. The tornado killed 7 in Parkersburg, and 2 in New Hartford.
2024 Greenfield tornado.
On the afternoon of May 21, 2024, a violent tornado tracked across southwestern Iowa, devastating the city of Greenfield. The tornado destroyed many structures and wind turbines across its path that stretched through Page, Taylor, Adams, and Adair counties, while also causing more than $31 million in property damage, killing five people and injuring 35 more. All the fatalities happened in the town of Greenfield. A doppler on wheels estimated wind speeds of 309–318 mph (497–512 km/h), making it the third highest winds recorded in a tornado in the United States, before the El Reno tornado, and the Bridge Creek tornado.