Perry told reporters Thursday that Ike is a gigantic storm, and says he "cannot overestimate the danger that is facing us."
Ike is expected to become at least a Category 3 storm with winds upward of 111 mph before it comes ashore. Hurricane warnings are in effect from the Louisiana coast to Morgan City.
Authorities are trying to avoid traffic gridlock similar to an evacuation during Hurricane Rita three years ago. Only eight zip codes in low-lying areas and near Galveston Bay are under mandatory evacuation orders.
Traffic is stacked bumper to bumper on one freeway leading away from Galveston County and into the Houston metropolitan area.