You want the sparks to fly this Valentine's Day, just not from a power line.

PG&E is cautioning all the lovebirds out there to make sure they tie down or weigh down mylar baloons.

The material they're made out of is a conductor, and if they get into power lines they can knock out electricity.

PG&E spokesman Nacho Ariquistain has seen it happen, right across from a vendor's stand.

"She was very surprised at the extent of the explosion she saw directly across from her. So yeah, that's what happens when these balloons get away from you," he said. 

Last year, more than 8,700 customers lost power in 38 outages caused by the metallic balloons. Some of them can last for hours depending on the damage to the lines.