Quinn issued a statement Monday saying he informed Department of Homeland Security Secretary Janet Napolitano of his decision.
Meanwhile, Sen. Dick Durbin and other lawmakers plan to meet with FEMA Director Craig Fugate on Wednesday to challenge the decision.
Quinn says Illinois is doing everything it can to help communities hit hard by storms on Feb. 29, including the Saline County town of Harrisburg, where seven people died and 98 homes were destroyed by an F4 tornado.
But he says some assistance needed by residents is available only through a federal disaster declaration.
FEMA says there's enough private insurance and other resources for Illinois to recover.