Music festivals have grown in number and popularity around the world in recent years, but this summer's festival season has been particularly notable for a spate of stage collapses.

A stage collapse before an Aug. 13 performance by Sugarland at the Indiana State Fair in Indianapolis resulted in at least six deaths. Another in Hasselt, Belgium, while the Smith Westerns performed at the Pukkelpop Festival, killed at least five last week.

Other incidents this summer include a video screen toppling during a Flaming Lips concert in Tulsa, Okla., and a stage roof coming down during a Cheap Trick performance at a festival in Ottawa, Canada.

Sudden storms and high winds were common factors in all the incidents.

Even as the popularity of music festivals grows, the extent to which standards for stage construction and event safety are applied varies by jurisdiction and venue, some industry experts say.

“When the municipalities or the venues look at a temporary structure, it's under the radar many times,” said William DesPres, risk engineering manager with Zurich North America in Lawrenceville, Ga.

“The whole thing with engineering these things is balancing cost and safety,” Mr. DesPres said.

“There are standards in the staging industry, especially at that level,” that address issues such as types of load, wind gusts and other factors, said James Chippendale, executive vp at Doodson Insurance Brokerage L.L.C. in Dallas.

He noted, however, that the “stage” often is a collection of components including backdrops, canopies, rigging, lights and video screens, each adding stresses to the overall system in conditions such as high winds. The interaction of those components must be considered in assembling an outdoor stage, he said.

“A lot of these past stage collapses, it's not so much the stage, it's everything else that goes on around the stage,” said Mr. Chippendale, who works with the annual Lollapalooza and Austin City Limits music festivals.

“Those could all be different vendors,” he said. At events presented by his firm's clients, the various vendors work together to understand how the different components affect one another.

“They're discussing it prior to the event. They're discussing it during the setup,” he said. “Most of these companies are all working together and safety is first and foremost in everybody's minds.”

Both stressed the importance of having a plan in place to deal with severe weather conditions, with graduated steps as weather conditions intensify, and sticking to that plan. “You definitely want someone to monitor the weather and you want to have a plan,” Mr. DesPres said.

At festivals he works with, “We are watching weather patterns, we are talking to the National Weather Service,” Mr. Chippendale said, with emergency measures in place to evacuate the field, the stage, etc. if weather conditions dictate.

He noted that there were weather issues at this year's Lollapalooza as a thunderstorm system approached Chicago the afternoon of Aug. 7.

“We were literally on the phone with all of the various entities talking about the storm that was approaching Chicago,” Mr. Chippendale said. “We were well-prepared to evacuate the park if need be, postpone shows, evacuate the stage fronts.”

As officials investigate the Indiana State Fair collapse, the first lawsuits in connection with the event were filed last week.

Fair officials reportedly had received an NWS severe thunderstorm warning and advised the audience of the possibility of severe weather, but the stage collapsed before an evacuation order was given.

Another outdoor performance in the area that evening—by the Indianapolis Symphony Orchestra at Conner Prairie—was canceled and the 7,000-person audience evacuated after officials received a weather advisory.

The fair's exposure to any claims apparently will be limited by Indiana law capping claims against public entities to $700,000 per individual and $5 million per occurrence. The fair is self-insured under that same Indiana code.

Mr. Chippendale acknowledged the frequency of recent stage collapses, but said it's important to view them against the increase in the number of outdoor music events.

“We've seen a rash of these in the last couple of years,” he said. “It looks like it's becoming more and more frequent, but if you look at the sheer number of outdoor events and outdoor stages that are set up, it's still a tiny, tiny percentage” of the total, he said.