A destructive tornado outbreak affected much of the Midwestern United States on April 21, 1967, in particular the towns of Belvidere and Oak Lawn, Illinois, United States. It was the largest tornado outbreak of 1967 and has been described by NWS Chicago as "Northern Illinois' worst tornado disaster". The outbreak produced numerous and significant (F2+) tornadoes, with ten of them in Illinois alone. Included was one of just six documented violent (F4/F5) tornadoes in the Chicago metropolitan area since the area was first settled.

Meteorological synopsis April 21, 1967 was a warm Friday afternoon in northern Illinois. Following a foggy morning with temperatures in the middle 50s °F, temperatures rose rapidly in the afternoon as low geopotential heights approached from the southwest. A warm front—part of a very deep shortwave trough—passed through Illinois all day and by afternoon moved north of the state. As a low-pressure area within an extratropical cyclone approached the area, temperatures rose into the low to mid 70s°F with dew points rising into the 60s°F, an upper-level jet reaching , and increasing low-level vertical shear. Meanwhile, a persistent mesolow feature near Joliet, Illinois, helped to maintain backed low-level winds from the south. +Outbreak death tollStateTotalCounty CountytotalIllinois58Boone24Cook33Lake1Totals58 As conditions became more favorable for tornadoes and supercells began developing in the Chicago area, the regional U.S. Weather Bureau office issued a tornado watch at 1:50 p.m. CDT covering the northern half of Illinois plus southern Wisconsin, eastern Iowa, and western Indiana. By 3 p.m. CDT/2100 UTC, more than 12 tornadoes had already been spawned from the storm system.

Confirmed tornadoes

F#LocationCounty Time (UTC)Path lengthDamageMissouri F0NE of Azen Scotland 1400 Tornado was observed on the ground but apparently caused no damage. F1NE of Gower Clinton 1830 Dust-laden tornado was seen but caused no damage. F1Cameron 1900 Tornado caused some damage in south Cameron. Condensation funnel was reportedly absent. F2E of Pattonsburg Daviess Tornado completely leveled all buildings except the house at one farm site and destroyed one wall of the house.Grazulis. p. 1088. Tornado may have formed from the same thunderstorm that struck Cameron, but the time does not suggest this. F0NE of Gallatin 1915 Brief touchdown failed to produce evidence of damage. F3N of Mandeville Ray, Carroll 1920 Tornado extensively damaged or leveled homes, barns, and other outbuildings. It also injured livestock. F2S of Humphreys Grundy, Sullivan 2000 Tornado destroyed eight homes, severely damaged seven others, and shattered glass windows as it hit Humphreys. Two children and a woman were injured in their trailer, as were four men sheltering inside a barn. Grazulis rated the tornado F3. F2NE of Cunningham Chariton 2010 Neither Grazulis (1991) nor Storm Data lists this tornado, suggesting that it was either weaker than F2 in intensity or never existed. F4NE of Sumner to W of Newark Linn, Macon, Knox 2020 Four homes and several barns were completely leveled while two people received minor injuries. Three or more funnels and erratic shifts in the damage path were reported to have occurred, suggesting that the long-tracked tornado was in fact a tornado family. F2W of Marshall to SE of Slater Saline This tornado may have actually included two or more touchdowns, implying that the single event was two or more tornadoes. It caused minor damage to a porch and to farm buildings along its skipping path. Grazulis did not rate the tornado as significant (F2+). F0W of Corder Lafayette 2103 Tornado did not cause any noticeable damage. F1NE of Adrian Bates 2110 Tornado produced minor damage to buildings and farm equipment.Indiana F1Rushville Rush 1833 F2NE of Commiskey Jennings, Jefferson 2310 Tornado unroofed and destroyed two homes, injuring two people, and then leveled a trailer and farm buildings. F0NE of Monticello White 0227 Tornado produced very minimal damage.Iowa F3E of Fairfield Jefferson 2000 Tornado never hit any structures and only briefly made contact with the ground. F2E of Birmingham to NE of Mount Union Van Buren, Hancock 2100 Tornado damaged 12 or more farms with only minimal F2 intensity at most. The damage path was very discontinuous, with only isolated patches of "extensive damage."Illinois F1SW of Spring Hill Whiteside 2130 F2E of Coal Valley to S of Hooppole Henry 2135 Numerous funnel clouds occurred with multiple reports of tornadoes. First tornado touched down north of Orion with isolated touchdowns to beyond Hooppole, with significant non-tornado-related wind damage. Tornado killed livestock, destroyed farm buildings, and uprooted trees. F2N of Hooppole 2150 Second Hooppole tornado leveled farm buildings and blew down large trees in rural areas. F4SW of Belvidere to N of Woodstock Boone, McHenry 24 deaths — See article on this tornado F1S of Daysville Ogle 2200 Tornado caused damage to many homes and downed trees while moving north, unlike other tornadoes this day which moved east-northeast. F2W of Maytown Lee 2202 Tornado severely damaged trees and farms and flipped a truck on Illinois State Highway 76 (now an Illinois route). F1SE of Amboy 2215 Tornado destroyed barns and blew down trees. Two distinct damage paths and funnel clouds observed, suggesting that a family of two tornadoes was involved. F1W of Kasbeer Bureau 2230 Tornado destroyed buildings on farms and scattered debris about. Almost went undetected but was observed by mushroom–gatherers. F2SE of Hennepin Putnam Tornado injured a man as it flipped two trailers and caused minimal tree damage. Grazulis (1993) did not rate the tornado as significant (F2+). F1SE of DeKalb DeKalb 2240 Two tornadoes touched down apart from each other but are listed as one tornado. One tornado damaged structures and broke glass and trees at Northern Illinois University while uplifting a roof to the south with $50,000 (1967 USD) roof damage. Second tornado damaged farms simultaneously about to the south, but with discontinuous damage. Probably a tornado family. F4NW of Middlebury to Lake Zurich to W of Hawthorn Woods McHenry, Lake 2300 1 death — See section on this tornado F2Elgin Kane 2310 Tornado destroyed one barn and caused roof and wall damage to Elgin State Hospital. Also badly damaged a factory. The state hospital sustained $100,000 in damages. F1NW of Bloomingdale DuPage Tornado briefly hit Keeneyville with little damage. F1Addison to Schiller Park DuPage, Cook Tornado skipped through several communities, including Franklin Park, with minimal damage. F4Palos Hills/Oak Lawn to Chicago South Side (entered Lake Michigan at 79th Street beach) Cook 2324 33 deaths — See article on this tornado F1Lincoln Park 2340 Tornado damaged an amusement park before moving over Lake Michigan. F1Champaign Champaign 0250 Brief touchdown on a farm. F2Geneva Kane, Cook unknown unknown Tornado struck 3 homes on the north side of Batavia before damaging 25 homes in Geneva. Some of the homes lost roofs and walls. 20 homes were also damaged in Streamwood.Michigan F2Casco to Dunningville Allegan 2355 Trailer and warehouse destroyed with many homes damaged. Minor injuries reported. Grazulis did not rate the tornado as significant (F2+). F3SW of Grandville to E of Ada Kent 2358 Struck the south side of Grand Rapids. 65 buildings were destroyed, and 60 others were badly damaged. 375 buildings sustained minor damage. A church and a K-Mart store were completely destroyed. F2NE of Middleville to NW of Lake Odessa Barry 0000 A house had its roof and kitchen ripped off. F2Derby Berrien 0025 School under construction leveled, pieces carried away. Several barns and outbuildings leveled as well. Grazulis did not rate the tornado as significant (F2+). F0S of Holton Muskegon 0110 A brief tornado touchdown in a rural area with other funnels also witnessed to have touched down. F2Portland Ionia 0115 Homes were unroofed in Portland, four barns were destroyed, and 40 cattle were killed. F4NE of Westphalia Clinton This violent destroyed buildings on 10 farms. Three homes were destroyed, 18 others were damaged, and 34 sheep were killed in 2 barns. Grazulis rated the tornado F3. F2N of Cascade Kent 0130 Rural outbuildings were destroyed along its path. Grazulis did not rate the tornado as significant (F2+). F1N of Sunfield Eaton 0148 Some farm buildings were destroyed. F2Potterville to Lansing Eaton, Ingham 0210 A barn and a Meijer store were destroyed, and the side of a house was torn off.

Belvidere, Illinois

This enormous and violent F4 tornado, which struck the Belvidere-Harvard-Woodstock area, was responsible for one of the highest tornado-related death tolls in a single school building ever recorded when it struck Belvidere High School as multiple school buses were being loaded. At 3:50 P.M., a violent multiple vortex tornado, later given an F4 rating, moved through Belvidere, Illinois, damaging the high school and overturning buses. A total of 24 people were killed with 13 of the dead in Belvidere at Belvidere High School, making this tornado the sixth deadliest ever to hit a school. 410 people were injured as well and 127 homes destroyed with another 379 being damaged. The Belvidere tornado was especially devastating because it hit the school just as students were getting on the buses to go home. Just before 4 p.m. CDT, the tornado reached the school. Twelve buses, already filled with elementary- and middle-school students, were tossed about. Several of the students were tossed into adjacent fields and killed. A bus driver was killed as well. Shortly after the passing of the tornado, faculty and some of the stronger students used the fireproof doors of the high school as stretchers to carry the injured into the cafeteria, the severely injured into the library, and the dead into the gymnasium. Four hundred cars (three hundred new cars and 100 employee cars) were destroyed at the Belvidere Assembly Plant. A school bus on a roadway south of Harvard was thrown into power lines and torn in half. The driver and students survived by sheltering in a ditch.

Lake Zurich, Illinois

This violent tornado, the second violent tornado of the day in Illinois, may have developed as far southwest as Elgin but was first observed at about 5:00 p.m. CDT near Fox River Grove, though its path is officially believed to have begun near Middlebury. It then produced a discontinuous damage path through Fox River Grove, North Barrington, and Lake Zurich. The most intense damage, given an F4 rating, occurred at Lake Zurich Manor, about northwest of downtown Lake Zurich; there, roughly 75 homes were leveled and 200 severely damaged. The Acorn Acres subdivision, northeast of and adjoining Lake Zurich Manor, reported scattered damage and debris with about 12 homes severely damaged. According to official plots from Storm Data, the tornado lifted after hitting Acorn Acres, though non-tornadic damages to trees and buildings occurred as far as the intersection of Illinois Route 63 and Gilmer Road. There, severe winds, possibly downbursts, destroyed four homes, one brewery, and a plastic-manufacturing site, though at least one source indicates that the tornado was likely still present at that place. In all, the tornado killed one person, and damaged 400–500 homes and destroyed about 100 other homes. An air-conditioning unit weighing was thrown . Cars were picked up and tossed as well.

Oak Lawn–Evergreen Park–Chicago, Illinois

This deadly, violent and horrific tornado was the deadliest tornado of the entire outbreak and the deadliest tornado to ever hit the metropolitan area of Chicago. The tornado that swept through Palos Hills, Oak Lawn, Hometown, Evergreen Park, and skipped through Chicago's Southside, killed 33 people. The path of this tornado was 16 miles long, and at times wide. It dissipated at Rainbow Beach on Lake Michigan.