Billie Eilish, by Charles Reagan Hackleman

After a relatively easygoing start to weekend one of Austin City Limits Music Festival on Friday, on the second day, the fest seemed to find its groove a bit more.

It may have actually been slightly hotter than the extremely hot day 1, but the atmosphere was markedly more upbeat and celebratory throughout Zilker Park. Perhaps that had to with the fact that the Texas Longhorns were playing—and hundreds of fans were gathered at the Beer Hall to watch and cheer them to victory against the University West Virginia Mountaineers.

But it might have also had a lot to do with a much younger crowd filling the park, many of whom were eagerly waiting to see Billie Eilish perform on the Honda stage later in the day.

Earlier on Saturday, Flora Cash kick-started the American Express stage with a glowing performance, easing fans into the busy day with their intimate tracks, all leading up to their big, singalong finale of their hit single "Somebody Else," which unsurprisingly drew cheers from those surrounding the stage.

Not long after, Taylor Bennett was performing on the nearby T-Mobile stage, delivering a high-energy set as he furthered cemented his standing in the industry and perhaps distinguished himself from older brother Chance the Rapper. 

Speaking of siblings, also performing an early afternoon set was FINNEAS, aka Finneas O'Connell, aka older brother of Billie (Eilish) O'Connell. And although he'd also join her later on, as he usually does, this was his moment to shine, as he performed his own material and proved why he is such a musical force in his own right. 

As the day went on, audiences were treated to vibrant, colorful performances from the likes of MisterWives, Hippie Sabotage and Sigrid, the latter of whom offered up a series of intimate ballads and shimmering pop cuts from her recent debut album. For many in attendance, this was likely their first time to see the young Norwegian singer live, and it was clear she was winning them over, if they weren't already fans.

By late afternoon, it was a trio of ladies lighting up the festival grounds, starting with an electric performance from Tierra Whack, who conquered the T-Mobile stage despite some serious heat-related issues with her DJ's equipment. Over at the Honda stage, Alabama Shakes frontwoman Brittany Howard absolutely soared as she debuted a lot of her new solo material live. Meanwhile, at the Miller Lite stage, Kali Uchis dazzled, enduring the blazing heat while adorned in a sequined balaclava.

On the T-Mobile stage, the party was just getting started as Judah & the Lion offered up a reliably massive performance, bring a much-needed surge of positive energy as the hottest temps of the day plastered Zilker Park. 

The energy level only increased as Billie Eilish, arguably the day's most anticipated acts, took the Honda stage. She was kinda-sorta billed as a headliner despite her 6 p.m., pre-sunset time slot, but the enormous swarm of adoring fans more than justified the headliner status, as it was clear a large portion of the day's attendees were crammed in around the stage, having intentionally come to the fest just to see the 17-year-old singer. 

From her opening with "Bad Guy" to closing with "When the Party's Over" and "Bury a Friend," Eilish had the crowd entranced. And while everyone was huddled closely, she still encouraged them to move around with her, at times commenting about how awfully hot it was, acknowledging she was definitely aware of the conditions fans were enduring to watch her play live.

As the sun set on Zilker, it was James Blake's turn at the helm of the Miller Lite stage, where he hypnotized onlookers with his moody, endearing renditions of fan favorites and some of his newer material, prepping the crowd for a relaxing finish to the evening.

And then came The Cure, closing out the Honda stage with a glorious performance, surrounded by a welcoming crowd of young and old fans. The nostalgia set in thick as the band played old favorites and treated the audience to a lush, simply mesmerizing set. While the band has played the festival in the past, they easily justified their placement atop this year's lineup with an incredible victory lap of a show.