DENVER -- It's rare that a power pole catches fire during a rainstorm, but it happened 12 separate times Thursday night.
Xcel Energy said the power poles ignited due to arcing. The company's spokesman, Mark Stutz, told Denver7 that conditions were just right for arcing.
"We had a long period of dry weather. We had dirt and other materials build up on our power lines... the (wet) dirt allowed the electricity to arc (or jump) off the line on the path of least resistance," he said. "Typically it will jump and for a brief moment it will strike the power pole."
Stutz said the electricity took the path of least resistance and arced from the insulators to power poles.
The resulting fires and other weather-related events left 30,000 customers without power.
Stutz said the grime typically gets washed off in rainstorms before it has a chance to built up and become an electrical conductor. He said an extended dry spell can lead to more buildup and then more arcing when it does rain.
One of the power pole fires led to the closure of I-270 Thursday night.
Commerce City Police say the lines across I-270, near Quebec, began sagging.
Rain was a problem Thursday night, but wind is expected to be a problem Friday night.
While wind can also cause arcing, Stutz said the biggest wind-related problem is that it can blow tree limbs onto power lines, knocking them down.