Record setting heat set the stage for an moderately unstable air mass, while a mid-level atmospheric disturbance provided the forcing and strong winds to develop scattered thunderstorms by late afternoon into early evening, some of which produced damaging winds and hail.
A strong micro-burst produced 80-100 mph winds and destructive hail in West Addison with a seasonal camp destroyed with one occupant receiving minor injuries. More than 15,000 customers were without power due to storms across VT.

Thunderstorm Wind in CHITTENDEN, VERMONT
From 18-MAY-17 16:29:00 to 18-MAY-17 16:30:00 (EST-5)
Location: ESSEX JCT
Magnitude: 50.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: NWS Employee

Strong thunderstorm winds estimated to be 50 knots or greater occurred across portions of Williston, especially north of Route 2A. Several reports of large tree branches of softwoods (pines/willows) downed by thunderstorm winds, causing power outages and minor structural damage.

Hail in RUTLAND, VERMONT
From 18-MAY-17 18:45:00 to 18-MAY-17 18:45:00 (EST-5)
Location: FAIR HAVEN
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Dime size hail reported.

Thunderstorm Wind in CHITTENDEN, VERMONT
From 18-MAY-17 16:25:00 to 18-MAY-17 16:25:00 (EST-5)
Location: (BTV)BURLINGTON ARPT
Magnitude: 50.00 MG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: ASOS

A measured wind gust of 50 knots was recorded at Burlington Int'l Airport along with scattered large branches of softwoods (pines) falling on property causing some damage.

Hail in ADDISON, VERMONT
From 18-MAY-17 17:27:00 to 18-MAY-17 17:28:00 (EST-5)
Location: ADDISON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Quarter-size hail reported along with strong gusty winds.

Hail in WASHINGTON, VERMONT
From 18-MAY-17 17:54:00 to 18-MAY-17 17:57:00 (EST-5)
Location: WARREN SUGARBUSH ARP
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail occurring for several minutes with sizes up to dime size or slightly larger accumulating an inch or more in portions of the area.

Hail in ORANGE, VERMONT
From 18-MAY-17 18:45:00 to 18-MAY-17 18:45:00 (EST-5)
Location: EAST CORINTH
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Dime size hail reported.

Hail in CHITTENDEN, VERMONT
From 18-MAY-17 16:28:00 to 18-MAY-17 16:30:00 (EST-5)
Location: WILLISTON
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Dime to nickel size hail observed for two minutes along with strong gusty winds near 50 mph that knocked down several limbs of a Willow tree.

Hail in ADDISON, VERMONT
From 18-MAY-17 17:32:00 to 18-MAY-17 17:32:00 (EST-5)
Location: ADDISON
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Dime size hail reported.

Thunderstorm Wind in ADDISON, VERMONT
From 18-MAY-17 17:18:00 to 18-MAY-17 17:25:00 (EST-5)
Location: WEST ADDISON
Magnitude: 78.00 EG
Property damage: 200.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

NWS survey team determined a microburst with winds estimated between 80-100 mph initiated across Lake Champlain and moved ashore on Potash Bay road with the maximum extent of damage occurring on Potash Bay road and Lake street. A summer camp was partial lifted from it's foundation and rolled onto it's side with neighboring homes witnessing some structural damage in terms of missing/damaged gutters and shutters. Dozens to hundreds of Willow and Pine trees were snapped or uprooted and damaging hail accompanied these winds.
A 75 year old female was in the camp at the time of the storm and received minor injuries.
Other, more scattered wind damage from this storm was along the lake shore in a 2-3 mile radius as well as east to Route 22A.

Thunderstorm Wind in CALEDONIA, VERMONT
From 18-MAY-17 17:00:00 to 18-MAY-17 17:00:00 (EST-5)
Location: EAST BURKE
Magnitude: 50.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Public

Trees and power lines down by thunderstorm winds.

Thunderstorm Wind in ORANGE, VERMONT
From 18-MAY-17 18:45:00 to 18-MAY-17 18:45:00 (EST-5)
Location: EAST CORINTH
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Huge trees downed by thunderstorm winds.

Thunderstorm Wind in RUTLAND, VERMONT
From 18-MAY-17 19:03:00 to 18-MAY-17 19:03:00 (EST-5)
Location: WELLS
Magnitude: 59.00 MG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Mesonet

Measured wind gust of 59 knots as well as some tree damage.

Thunderstorm Wind in CHITTENDEN, VERMONT
From 18-MAY-17 16:35:00 to 18-MAY-17 16:35:00 (EST-5)
Location: NORTH WILLISTON
Magnitude: 50.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: NWS Employee

Strong thunderstorm winds downed large tree branches onto power lines in eastern Williston.

Thunderstorm Wind in ORLEANS, VERMONT
From 18-MAY-17 16:30:00 to 18-MAY-17 16:30:00 (EST-5)
Location: BARTON
Magnitude: 55.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Tractor trailer blown over on Interstate 91 as well as trees blocking railroad tracks.

Thunderstorm Wind in ESSEX, VERMONT
From 18-MAY-17 17:18:00 to 18-MAY-17 17:18:00 (EST-5)
Location: MAIDSTONE
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Utility Company

Trees and power lines down by thunderstorm winds.

Hail in ADDISON, VERMONT
From 18-MAY-17 17:18:00 to 18-MAY-17 17:20:00 (EST-5)
Location: WEST ADDISON
Magnitude: 1.50 
Property damage: 50.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A destructive hail storm and destructive thunderstorm winds caused considerable damage along Potash Bay road and Lake street. Hail stones of 1 to 1.5 inches in diameter blown by 60-80 mph winds produced numerous holes in siding, dents on vehicles and broken windows in the most severe occurrence on Lake street. Hail damage as witnessed in this survey is highly unusual in Vermont and northern NY.

Thunderstorm Wind in CHITTENDEN, VERMONT
From 18-MAY-17 16:35:00 to 18-MAY-17 16:36:00 (EST-5)
Location: NORTH WILLISTON
Magnitude: 50.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: NWS Employee

Strong thunderstorm winds downed several large tree branches and a few soft wood trees (pines) on Sandhill road and nearby neighborhoods in Essex, causing power outages.

Thunderstorm Wind in ESSEX, VERMONT
From 18-MAY-17 16:50:00 to 18-MAY-17 16:50:00 (EST-5)
Location: BLOOMFIELD
Magnitude: 50.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Utility Company

Trees and power lines down by thunderstorm winds.

Thunderstorm Wind in ESSEX, VERMONT
From 18-MAY-17 17:00:00 to 18-MAY-17 17:00:00 (EST-5)
Location: ISLAND POND ARPT
Magnitude: 50.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Utility Company

Trees and power lines down by thunderstorm winds.