The areas affected included homes near 5600 South and 2300 West.
Crews with Rocky Mountain Power said rain helped contaminants on the power lines seep into insulators. The mixture created a spark and started a fire on the electricity pole.
According to a crew member, the power line insulators are old, which makes them vulnerable to contaminants every time it rains.
Roy City fire crews put out the small blaze, but dozens of people were left in the dark while crews worked to repair the outage overnight.
A neighbor said he helped extinguish the flames with a water hose.
No injuries were reported.