Many of the company's multiplayer servers were based in New York City, which has experienced heavy flooding and loss of power in the wake of the storm.
"We are aware of connectivity issues with some of our titles. Our data centre is being affected by extreme weather conditions on east coast," Activision said today (October 31) through its support Twitter account.
"We are working to resolve them as quickly as possible. We will keep you updated. Thank you for your patience."
Games affected by the outages include Call of Duty: World at War on all systems, Call of Duty: Modern Warfare 2 on PS3, Call of Duty: Black Ops on PS3, PC and Wii and all Guitar Hero titles on all systems.
The next game in the series, Call of Duty: Black Ops 2 will be available on Xbox 360, PS3 and PC from November 13 worldwide. A Wii U version will be available at the system's launch on November 18 in North America and from November 30 in Europe.
Watch the live-action Black Ops 2 trailer below: