It happened around 7:30 p.m. in the 17500 block of FM 1485 northwest of New Caney near Lost Lake Drive.
The 17-year-old was resetting the flag-type banner in front of an appliance business when it came into contact with the lines, estimated to be carrying 33,000 volts of electricity, according to the Montgomery County Sheriff's Office.
Medics worked for close to 20 minutes and were able to revive the boy at the scene before he was transported to Kingwood Hospital.
At last report, the teen was still in critical condition.