The announcement was made by Governor Kay Ivey on Monday afternoon.
She said: “Alabama is once again in the path of a hurricane, but I know Alabamians will once again come together and be prepared for whatever Michael may bring.
“On the state level we are prepared, and now is the time for residents in south Alabama to review your emergency preparedness plans and also get prepared.
“Most importantly, heed all warnings and instructions from local authorities.”
Hurricane Michael is expected to crash into the coast of Florida and Alabama on Wednesday.
The storm could grow to a Category 3 hurricane before it reaches land.
Governor Ivey justified her decision via an official press statement.
She explained the hurricane will cause “substantial risk of physical injury or death” as well as threatening to “disrupt essential utility services and systems”.
In response, Governor Ivey announced that the Alabama National Guard had been placed on standby, and that the Alabama Emergency Management Agency State Operations Centre will be activated.
She added on Twitter: “Now is the time for residents in south Alabama to review your emergency preparedness plans and also get prepared.”
A state of emergency has separately been declared by the state of Florida, which is expected to bear the brunt of the storm.
Florida Governor Rick Scott said: “Our state understands how serious tropical weather is and how devastating any hurricane or tropical storm can be.
“As we continue to monitor this storm’s northward path towards Florida, it is critically important that our communities have every available resource to keep everyone safe and prepared.
“If any Florida family doesn’t have an emergency preparedness plan, now is the time to act.”
Governor Scott also ordered the activation of the Tallahassee State Emergency Operations Centre to coordinate the response.
A hurricane warning is currently in place from the Suwannee River in Florida to the Florida/Alabama border.
Hurricane Michael is gaining strength and is expected to become a major hurricane within the next 24 hours.