Figure 1 depicts the surface observations at 8:00 am EDT, which shows a cold front moving across the Great Lakes, which brought southerly winds to Massachusetts. Pre-frontal thunderstorms likely initiated in the morning hours of July 5th, which ultimately led to this tornado.

The Chesterfield, MA F1 tornado of July 5, 1984 impacted Hampshire County in Massachusetts. According to NOAA (2019), the F1 tornado caused no fatalities or injuries, but caused $2500 dollars in property damage. The tornado touched down near Smith Road at 2:30 pm EDT. The tornado travelled for 0.3 miles and had a maximum width of 30 yards.
Sources
NOAA Central Library. (2020). U.S. Daily Weather Maps. Thursday July 5, 1984 [PDF]. Retrieved from https://library.noaa.gov/Collections/Digital-Collections/US-Daily-Weather-Maps
NOAA National Centers for Environmental Information (2019). Storm Events Database. Retrieved from: https://www.ncdc.noaa.gov/stormevents/