Severe weather and high winds toppled power poles and downed power lines on both sides of the lake Thursday afternoon.
Up to 12,000 residents and businesses were left in the dark by the thunderstorms.
At the peak of the outage, Entergy Louisiana and Entergy New Orleans reported about 2,000 customers without power, mainly in the New Orleans East and on the Westbank of the city.
The outages were more pronounced on the Northshore.
The Washington-St. Tammany Electric Co-op reported that the storms caused 3,800 members in St. Tammany to lose power.
A spokesman for WST said there were many poles down due to the wind, and he didn't have an estimate of when a majority of customers would be back online.
Cleco also reported many customers without power due to the storms. A Cleco spokeswoman said that 6,500 customers in St. Tammany lost power due to the severe weather.