Don’t get it twisted: trees are a crucial lifeline during a severe heatwave like the one gripping the US right now. So the tree trimming controversy that unfolded this week during the screenwriters and actors strike is anything but trivial.

In case you missed it, union members of the Writers Guild of America (WGA) and the Screen Actors Guild – American Federation of Television and Radio Artists (SAG-AFTRA) joined picket lines outside Universal Studios despite temperatures soaring above 90 degrees Fahrenheit this week. In a tweet that went viral, writer Chris Stephens pointed out on Monday that trees that would have shaded the protesters were suddenly quite bald.

The allegations of maliciously timed tree trimming triggered an investigation by Los Angeles City Controller Kenneth Mejia. They’re LA City-managed street trees, after all, and his office announced yesterday that the city hadn’t issued the necessary permits that would have given NBCUniversal the green light to trim them. City agencies are still looking into whether the case “warrants the issuance of an administrative citation or hearing.”

“Trees are essential to providing Angelenos with significant environmental and public health benefits, especially during a heatwave,” Mejia tweeted.

NBCUniversal didn’t immediately respond to a request for comment from The Verge, but it told the Los Angeles Times, “The safety tree trimming of the Ficus trees we did on Barham Blvd. has created unintended challenges for demonstrators. That was not our intention.” NBCUniversal told Deadline it prunes the trees each summer, although Mejia’s office said that trees ought to be trimmed every five years and that the city hadn’t issued permits for this location in the past three years.

Heat sickness is no joke — it’s actually the top weather-related killer in the US, taking a heavier toll than tornadoes, hurricanes, and floods. Los Angeles also happens to be a “heat island,” a term that’s used for cities that are hotter than surrounding areas because urban sprawl tends to trap heat. Trees counteract that effect by providing shade and releasing moisture from their leaves that can cool the surrounding air. Shade alone can keep surfaces 20–45 degrees Fahrenheit cooler than other parts left in the sun.

SAG-AFTRA joined the strike roiling Hollywood last week, expanding a fight started by WGA writers for better pay and protections from AI. The heat is proving to be an unlikely adversary for picketers, forcing SAG-AFTRA to end protests outside Disney and Warner Bros. early on Monday. More than a third of Americans are under a heat alert today, and the “prolonged and dangerous” heatwave bearing down on much of the Western and Southern US is forecast to linger throughout the week. So if picketers plan to stay out on the streets, they’re going to have to find ways to beat the heat.

Disclosure: The Verge’s editorial staff is also unionized with the Writers Guild of America, East. Comcast, which owns NBCUniversal, is also an investor in Vox Media, The Verge’s parent company.