Tornadoes · United States · Massachusetts · 1787

Unrated tornado, Northborough/Southborough/Framingham, MA, August 15, 1787

Name: Unrated tornado, Northborough/Southborough/Framingham, MA, August 15, 1787
Start: 1787-08-15
Location: Northborough/Southborough/Framingham, MA

This Unrated tornado struck Northborough, Southborough and Framingham, MA on August 15, 1787. Its path ran 10.0 miles and was up to 200 yards wide. It killed nobody and injured 2. Before 1950 the record is Thomas P. Grazulis’s list of significant tornadoes: those rated F2 or stronger, and weaker ones that killed somebody.

The rating scale

Tracks are drawn in the color of the rating. Grazulis rated these tornadoes on the Fujita scale decades after the fact, from written accounts of the damage. The scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.

F040 to 72 mph
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
F173 to 112 mph
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
F2113 to 157 mph
Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.
F3158 to 206 mph
Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.
F4207 to 260 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
F5261 to 318 mph
Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.
Unratedthis tornado
Grazulis gave no rating: the surviving account records a tornado without enough about the damage to rate it. Almost all of these are before 1880.

The record

Rating: Unrated: the account is too thin to rate
Date: August 15, 1787
Time: Not recorded; the account gives the date only
Places named: Northborough/Southborough/Framingham, MA
Path length: 10.0 miles (16.1 km)
Path width: 200 yards (183 m)
Deaths: 0
Injuries: 2
Counties crossed today: Worcester and Middlesex counties
Drawn from: 42.32, -71.63
Drawn to: 42.29, -71.44
Record: Tornado Archive TPGB25

How the track was drawn

Tornado Archive drew the path as a straight line from the first place Grazulis names to the last. The tornado itself will not have run straight, and the line can miss a town it hit. The counties are today's, and many had other lines, or did not exist, in 1787.

What is not here

The warnings: The Weather Bureau issued its first public tornado forecasts in 1952. The warning archive this site reads begins in 1986.
The outlook: SPC's archive of convective outlooks begins in 1987.
The radar: Weather radar did not watch storms until after the Second World War. The radar archive this site reads begins in 1991.
The Weather Service's narrative: The Storm Events Database, with its narratives and casualty records, begins in 1950.
A damage survey: The Fujita scale dates from 1971, so no tornado before it was rated at the time. The rating here is Grazulis’s, from the accounts.
A sounding: The upper-air archive this site reads begins in the middle 1940s.
Surface observations: The record gives no time to match the observations to.

The other tornadoes of August 15, 1787

4 more significant tornadoes are on record that day.

Date	Time	Rating	Where	Path (mi)	Width (yd)	Deaths	Injuries
August 15		Unrated	E East Windsor, CT	5.0
August 15		Unrated	Rochester, NH				2
August 15	1:30 PM EST	Unrated	New Britain/Newington/Wethersfield, CT	5.9		2	10
August 15	5:00 PM EST	Unrated	Killingly, CT/Gloucester, RI to Mendon, MA	24.4	200		1

This ground now

The live radar over the track Every 1787 tornado in Massachusetts Every tornado in Massachusetts Warnings in force in Massachusetts now

About the record before 1950

Significant tornadoes only: Grazulis listed tornadoes rated F2 or stronger, and weaker ones that killed somebody. Most tornadoes are weaker than F2, so the list holds a fraction of the tornadoes that happened.
The early years are thin: A tornado is on record only where somebody saw it and wrote it down. The count rises through the 1800s with settlement and newspapers, not with the weather.
Rated from accounts: Grazulis rated each tornado decades later from newspaper reports, Weather Bureau records and local histories, not from a damage survey.
The tracks are reconstructed: Tornado Archive drew each path through the places Grazulis names, most often as a straight line from the first to the last. A track can miss a town it hit, and a tornado with one named place is a point. The counties are today’s.
A separate record: SPC’s database, from 1950, counts every confirmed tornado of any strength. The two are kept apart on every page and never added together.

What this means

Ratings are Grazulis's, read from written accounts of the damage; the rating scale is above. About the record before 1950 says what it holds and what it leaves out.

Sources

Thomas P. Grazulis, Significant Tornadoes 1680-1991 and Significant Tornadoes 1880-1989, as digitized by Tornado Archive (Maas and others, 2024). Public domain. Counties assigned by this site from today’s NWS county lines.