Wind gusts up to 60 miles per hour with tropical storm-force winds could whip through starting Monday morning and into Tuesday, forecasters said.
Governor McMaster says nothing has changed regarding the evacuations on Beaufort, Colleton, and Jasper Counties.
The state of emergency now includes all 159 counties in Georgia.
McMaster said those in the barrier islands in Beaufort, Colleton and Jasper counties of SC were told to leave by 10 a.m.
In Atlanta, people nervously watched towering oak trees as the city, 250 miles inland, experienced its first tropical storm warning.
Mayor John Tecklenburg said there were no serious injuries and the city would be back to normal Wednesday.
In the Jacksonville area, close to the Georgia line, storm surge brought some of the worst flooding ever seen there, with at least 46 people pulled from swamped homes.
"This is a serious storm", he said. Other forecasts show Irma dumping between 3 and 6 inches of rain in north Georgia on Monday and Tuesday. Associated Press reporters Kim Chandler in Montgomery, Alabama, John Raby in Charleston, West Virginia, Seanna Adcox in Columbia, South Carolina, and Kate Brumback and Bill Barrow in Atlanta contributed to this story. "Of course, we discharge and transfer those that we can", MUSC spokeswoman Heather Woolwine said.
So where should evacuating residents go?
Deal also issued a mandatory evacuation order for all areas east of I-95, all of Chatham County and some areas west of I-95 that could be impacted by potential storm surge from Hurricane Irma.
"Just because the weather appears to be calm now, don't take that for granted", Deal said during a Friday news conference.
A direct hit from Irma appeared increasingly unlikely in North Carolina, where emergency officials urged people to stay vigilant with preparations. After enduring heavy flooding in 2015, they said they didn't want to take any chances.
The Weather Service's official forecast for the Rock Hill area is for showers from Hurricane Irma to arrive late Sunday night.
While Matthew's destruction was largely confined to coastal areas, Irma had a much wider path of damage. "So I'm sticking with my final decision and we're out of here".
- Storm surge warnings in Florida, Georgia and SC mean "there is a danger of life-threatening inundation", the hurricane center said. "We will continue monitoring Hurricane Irma's path in the days ahead and coordinating with our federal, state and local partners".
Electric service to almost 1 million Georgia Power customers was impacted at the height of Hurricane Irma, and less than 24 hours later, Georgia Power has restored power to approximately 405,000 customers across the state. The current forecast has Jose coming about 500 miles away from the SC coast by Sunday, moving due north and staying well offshore.