Before 1850
- June 14, 1648: A "great tempest" downed trees somewhere in present-day Hartford County.
- June 20, 1682: A violent storm, including one or more likely tornadoes, devastated forests in southern Connecticut, affecting areas north of Fairfield across the Housatonic River before passing out into Long Island Sound between Milford and New Haven. The damage was worst around present-day Shelton, where a path was cut a half-mile wide where there was "scarce a tree left standing".
- 1728 or 1729: A possible tornado passed through New Britain and/or Wethersfield.
- August 17, 1784: Two tornadoes struck central Connecticut. The first tornado touched down near present-day Roxbury, then known as "Shipague-Neck". It travelled through the village of South Britain, injuring five people, with one man injured so that "his life was in great danger". Ten houses, five barns, and three mills were badly damaged or destroyed. The second tornado injured one person while moving down a hillside west of Southington.
- August 23, 1786: As many as six tornadoes did a great deal of damage in Windham County. Twenty homes and sixty-three barns were destroyed, as well as 1,000 acres (4.0 km2) of dense forest. One woman was killed and five people were injured in Woodstock. Leaves from destroyed trees rained down heavily in Providence, Rhode Island.
- August 15, 1787: The Four-State Tornado Swarm of 1787 was the largest tornado outbreak recorded to date, and affected most of New England. The first in the state touched down around 1:30 PM near New Britain, traveling along nearly the same path as a tornado in 1728 or 1729. This tornado was nearly as violent as the Wallingford Tornado of 1878. A mother and two of her children were killed in Wethersfield, and 10 others were injured before the tornado lifted outside of the town. What may have been another tornado caused additional damage as far east as Coventry. Another tornado struck East Windsor, damaging several homes and barns. Yet another touched down near Killingly, moving northeast into Rhode Island and Massachusetts.
- June 19, 1794: A tornado destroyed several structures in Milford injuring four people, while a separate tornado cut through Branford. A strange incident was recorded where a tree was uprooted and carried, fully upright, along a road in New Milford, along with several other large objects. A barn door was found 10 miles (16 km) from its source. Some loss of life likely occurred from one or both tornadoes.
- October 8, 1797: A tornado touched down in North Salem, New York, moving into Fairfield County. Six people were injured in Ridgefield, and possible tornado damage continued as far as Long Island Sound in Branford.
- August 2, 1799: A tornado destroyed two houses in New London County, affecting the towns of Franklin, Lebanon, and Bozrah.
- June 30, 1808: One or more tornadoes moved from Windsor to Coventry, killing one person.
- July 22, 1808: Trees and buildings were damaged by a tornado which moved from East Windsor to North Bolton.
- July 16, 1810: A tornado produced damage in or around Somers.
- August 1, 1812: A tornado passed from Westchester County, New York into Greenwich.
- July 22, 1817: Tornado produced tree damage from Woodbury to Watertown.
- August 13, 1817: A tornado destroyed 23 buildings in Wallingford.
- August 14, 1820: A tornado touched down east of Norwalk.
- June 3, 1836: A long-lived tornado tracked 30 miles (48 km) from Dutchess County, New York to Salisbury, seriously injuring many people.
- July 31, 1839: Six homes were damaged or destroyed on the west side of New Haven. A "heavy rumbling noise" was heard throughout the city.
- August 7, 1839: A possible tornado passed through a then-uninhabited area of Wallingford.
- August 14, 1840: A possible tornado struck Woodbridge.
Read more about this topic: List Of Connecticut Tornadoes