Weather Watch

Windblown Mylar balloons pose risks to wildlife and power lines

PG&E lineman Jacob Bell removing metallic balloons from power lines Friday.
PG&E lineman Jacob Bell removing metallic balloons from power lines Friday. Special to The Tribune

Valentine’s Day often means flowers and chocolates. Balloons are one of the ways to show your valentine just how much you care. Unweighted balloons — particularly metallic ones — can cause lots of problems, however, and here’s why.

A strong area of high pressure over the Great Basin this Super Bowl weekend will continue to produce gusty Santa Lucia (northeasterly) winds that can drive these loose balloons out to sea.

When Mylar balloons climb between 3,000 feet and 7,000 feet, they either explode or lose their “lift” and fall into the ocean. Unfortunately, oceanic creatures, such as sea turtles, can mistake these balloons for food. When eaten, they clog their intestinal tracts, causing them to starve.

Over land, Jay Snow, a park ranger, retrieves Mylar balloons from Death Valley National Park. At 282 feet below sea level, it is the lowest point in the United States. It’s also the hottest; the valley reached a record 134 degrees July 10, 1913. This park is a land of fierce beauty with magnificent landforms surrounded by snowcapped mountains.

“You hike for miles through this vast wilderness area and discover a canyon, a canyon that only a few people have probably walked before, but like clockwork you come across one of these metallic balloons,” Snow said.

One of his fellow rangers has found so many of these colorful chromelike spheres with “happy birthday” written in joyful letters along the top that he wallpapers the inside of his cabin with them.

Two types of balloons — Mylar and latex — are in use today. Mylar balloons are made with Mylar nylon, a material not classified as biodegradable. They often are coated with a metallic finish that conducts electricity.

On the other hand, latex balloons are elastic and are composed of natural rubber that is biodegradable. Latex weather balloons — the kind launched from Vandenberg Air Force Base — are filled with helium and are about 4 feet in diameter at sea level. These balloons rise through the atmosphere and expand in diameter.

By the time they reach about 100,000 feet, they expand to about 40 feet in diameter. Air temperatures at this altitude can drop to 50 degrees below zero or lower and freeze the latex. At this high altitude, a frozen balloon undergoes “brittle fracturing” and ruptures into small shreds of rubber that fall to earth.

This fact is key to understanding how so many Mylar balloon find their way to Death Valley. For most of the year, the winds blow from the Pacific Ocean over Los Angeles toward the east at elevations typically below 6,000 feet. These “onshore” winds carry Mylar balloons that have broken free or have been released from the greater Los Angeles area and find themselves on a journey toward Death Valley.

Easterly winds are predominant in late fall and winter and may be transporting these balloons from the Las Vegas area. In both of these scenarios, the winds that are carrying these balloons hit the windward slopes of mountains that surround most of Death Valley and quickly rise. The balloons are lifted to their bursting point and fall to the valley floor.

Not only do these metallic balloons litter pristine wilderness areas, but they also are a major cause of power outages. When these metallic balloons come in contact with electric power lines, they often cause outages. When metallic balloons get tangled in power lines, it has the same effect as if a wrench came in contact with both the negative and positive terminals of a car battery. It can cause power lines to short out, which can trigger the conductor to break, resulting in energized lines falling to the ground.

On average each year, metallic balloons that drift into PG&E power lines cause 300 outages and affect electric service to more than 165,000 homes and businesses throughout Northern and Central California.

To reduce this number and to help ensure that everyone can enjoy this Valentine’s Day, PG&E reminds customers to follow these safety tips for metallic balloons:

• “Look Up and Live!” Use caution and avoid celebrating with metallic balloons near overhead electric lines.

• Make sure helium-filled metallic balloons are securely tied to a weight heavy enough to prevent them from floating away. Never remove the weight.

• When possible, keep metallic balloons indoors. Never permit metallic balloons to be released outside.

• Do not bundle metallic balloons together.

• Never attempt to retrieve any type of balloon, kite or toy that becomes caught in a power line. Leave it alone and immediately call PG&E at 800-743-5000 to report the problem.

• Never go near a power line that has fallen to the ground or is dangling in the air. Always assume downed electric lines are energized and extremely dangerous. Immediately call 911 to alert the police and fire departments.

John Lindsey’s column is special to The Tribune. He is PG&E’s Diablo Canyon marine meteorologist and a media relations representative. Email him at or follow him on Twitter @PGE_John.