City utility director Chris Brewton said the combination of low rainfall and cold weather is "the worst of all cases," according to the Daily Sitka Sentinel.
The cold weather means the demand for power is growing. The city has asked residents to switch to a nonelectric heat source, such as oil, especially during peak-use hours in the morning.
The city's hydroelectric plants rely on Green Lake, south of Sitka, and Blue Lake, east of town.
"The good news is we're not burning diesel at this time," Brewton said. "We're right on the edge, but we haven't started."
The city uses a traffic light to illustrate its power status. On Friday, the city switched that light from yellow to red.
"Energy conservation is critical to reduce system load and minimize the amount of diesel generation that will be required during this period," Brewton said.
Brewton said the city could be forced to spend money to fuel the diesel generators, and the residents will have to bear that cost.
Brewton said the city continues to see a "normal load growth" -- mainly customers switching to electrical heat -- which is putting pressure on the hydroelectric system.
Brewton noted that on Friday he was approached by two customers who had plans to install 27-kilowatt boilers in their homes.
The advisory asking residents to switch power sources could remain in effect until mid-April.
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