It happened at a building in the 9200-block of Gross Point Road just before midnight.
Firefighters said someone left food unattended while cooking on the fifth floor, sparking the fire, which was contained to one unit.
No one was hurt, Skokie Fire Chief Jeff Hoeflich said.
But the real problem is the water damage.
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"My apartment's got it in the hallway; it's got into my apartment," resident Michelle Carelli said. "I'll have some cleaning to do in my apartment."
The water got into the electrical system, so the power had to be shut off for the more than 100 people living there.
"One room set off sprinklers, and now the whole building's affected," one resident said.
Firefighters said they hoped power could be restored Saturday morning and that they were working with Cook County Emergency Management to do so.