An early morning thunderstorm with unusually frequent cloud to ground lightning moved eastward across the western suburbs of Boston and then directly across the city. In Weston and Newton, several trees and power lines were knocked down by strong winds. Lightning strikes blew out transformers and knocked out power to an estimated 20,000 customers from Sudbury to Boston. Small hail was reported by the National Weather Service at Logan International Airport in Boston. The Boston Fire Department reported its busiest two hours on record as lightning strikes cut off power, triggered alarm systems and heavy rain flooded roads. Lightning detection systems recorded around 20 cloud to ground strikes per minute or around 1,200 strikes per hour, continuing for more than an hour.