Netflix and Pinterest restored service by Saturday afternoon.
Instagram used its Facebook fan page to communicate with users of its photo-sharing service. It posted a message on Saturday morning that blamed the electrical storm for the outage and explained that its engineers were working to restore service.
Still, many Instagram's users were searching for answers. "Instagram" was the top search term on Google on Saturday, according to Google Trends.
Netflix, Pinterest and Instagram are customers of Amazon Inc.'s web services division. The unit provides web services and data storage facilities that are commonly used for "cloud computing".
Amazon spokeswoman Kay Kinton told The Associated Press in an email that the storm cut power to some of company's operations. Service has been restored for most customers, Kinton said.
Netflix, a video streaming service, said on Twitter that subscribers should reconnect if they still experienced problems.
The online scrapbook service Pinterest says employees are working to fix remaining issues that may affect performance.
The Friday evening storms knocked out power for millions of people.