The south and western regions of Sao Paulo were hardest hit, according to Eletropaulo, the local power authority, speaking to local media.
More than 8,000 lightning strikes and winds of up to 53 mph (85 kilometer per hour) were recorded during the storm.
Local authorities said at least 70 trees came down on Monday alone in the city of 12 million inhabitants, although the actual figure is thought to be higher.
"The (power) network has been seriously damaged. Every tree that falls equates to hundreds of branches that damage wires and cables,” Eletropaulo’s vice-president Sidney Simonaggio told the G1 news portal.
Torrential rain also caused at least 30 major floods in the city and problems were reported with more than 150 traffic signals.
Engineers have been battling to fix damage caused by this storm and recent ones.
Before Monday's storm, the local government said at least 900 trees had fallen in a string of vicious weather systems in the last two weeks, one of which registered winds of nearly 62 mph (100 kilometers per hour).
More heavy rain is expected Tuesday evening.
During Brazil's summer, storm cells are frequently seen in the southeast region of the country, affecting São Paulo and Rio de Janeiro states, among others. It is not uncommon for huge hailstones to accompany the storms, despite temperatures in the mid to high 90s Fahrenheit (30s C), causing infrastructure and property damage.