Mother’s Day and graduation celebrations call for outdoor gatherings. But before firing up the grill, be sure to take precautions to ensure any Mylar balloons used to liven up the festivities won’t pose a threat to the electric system. In recognition of National Electrical Safety Month, Eversource is reminding customers that Mylar balloons can cause power outages and even pose a significant safety risk. “The silver metallic coating on Mylar balloons is a conductor of electricity. If the balloon makes contact with power lines, it can damage electric lines and equipment, and cause power outages.