As is the case with any outdoor music festival -- or anything else held in the city of Chicago -- sometimes the actual meat of any particular goings-on can be overshadowed by the weather that serves as its backdrop.

As it happened last year when a series of downpours soaked Lollapalooza to the bones, the 2012 edition is sure to be at least partially defined by the incredibly oppressive heat. Temperatures Friday, the festival's opening day, hit 95 degrees, the hottest temperature Chicago has seen in August in six years, leaving the 100,000 concertgoers who packed in Grant Park on the mega-fest's first day caked in sweat.

(Scroll down to view 2012 Lollapalooza festival photos.)

Ah yes, the six-digit crowd, the other story that tends to threaten on-stage happenings at Lolla. This year, the sold-out festival's organizers appear to have managed to squeeze even more people into the gates. Lines for nearly everything are atrocious, most concerning of which, even the water stations created bottleneck situations at numerous points around the grounds, particularly those near the bigger stages. With another hot (and likely stormy) day ahead Saturday at Grant Park, difficulty gaining access to water is a serious matter.

Crowds and heat aside, however, Friday at the festival was a day packed with strong performances from a range of impressive acts. As a one-man HuffPost crew attempting to cover a festival grounds that spans eight stages, 115 acres and endless musical micro-genres, I cannot claim authority when it comes to knowing what went down during every act at every stage. Below are some highlights -- and photos -- from the action. Let us know what we missed in the comments!

Glitter, glamour and rock: Upon entering the festival grounds at Congress Parkway, I immediately recognized the soft croon of Emily Haines, the songstress behind Canadian indie rock veterans Metric, and followed it through the already-dense crowds to the fest's north end. The first time I ever saw this band play, it was before a 400-person capacity club six years ago. In that time, Haines and her band have come so, so far.

Wearing a glittering vintage top and sparkly gold sunglasses under the hot sun, Haines led her men through a mix of songs off the recently released "Synthetica" and even brought out some of their classics including "Empty" and a jammy "Dead Disco." All the while, Haines captivated the crowd with her aerobic-bordering-on-frenetic dancing that rivaled the exuberance of the hard-to-top stageside ASL interpreters. A phenomenal set from a phenomenal band.

Dead zone: Though it's early in the festival, cell coverage is already incredibly spotty at best, a perpetual problem at this festival. I wonder how the suburban tweens -- not to mention my fellow social media-obsessed journalists -- are dealing with their inability to tweet.

SBTRKT plus skulls: Caught the tail end of Aaron Jerome, a.k.a. SBTRKT, on the shady Google Play stage. Joined by a live drummer -- take that, drum machines! -- Jerome's songs soared amid the early evening heat and I caught a number of people dancing uncontrollably once he launched into a spirited take on his biggest hit "Wildfire." After taking advantage of the shade to re-apply sunscreen -- prompted by the sight of more than a few advanced-stage sunburns -- Band of Skulls take the stage in monochrome black. Their bluesy songs slither with sinister sensuality like good whiskey-slamming music. And though their jams are optimized for dark bars, they translated just fine when daylit.

Where's the passion? It's pretty widely known at this point that Passion Pit lead singer Michael Angelakos has been having a difficult time as of late. Through much of the band's set Friday, Angelakos' falsetto felt wobbly and off-key at times, and many of the songs themselves lacked the excitement and drive of their studio versions. The band is known for having an energetic live show, so one wonders if they needed more time to finesse their set before returning to such a high-profile stage. Whatever the case may be, the band's new album, "Gossamer," is a gem and we're wishing Angelakos the best as he continues to recover.

'I'm a cool mom.' I think the BMI stage, with its Lake Michigan backdrop and tree-heavy surroundings, might be my favorite of the entire Grant Park grounds. Due to its location, it tends to be overlooked by the throngs, which allows the music to truly remain the center focus. Taking the stage around 6:50 p.m. Friday was singer-songwriter Dev, who screamed, "Who's ready to have some fun?!" as she launched into her unpretentious, bass-heavy jams. By the time she got to "Like a G6" (the Far East Movement song which samples her "Booty Bounce"), she held the audience in the palm of her hand. A woman who had the "cool mom" look down was dancing unabashedly in the back of the crowd caught my eye. Unpretentious, refreshing and, yes, fun.

Politely elegant. Arriving on the southern end of the Lolla grounds for the first point of the day, it was immediately clear that the two bands ending Friday on the southern big stages -- M83 and the Black Keys -- were high-profile attractions for ticketbuyers. At the Sony stage, the crowd packed in tight for Anthony Gonzalez and his electropop outfit, Opening aptly with "Intro," Morgan Kibby took over Zola Jesus' guest vocal and it all sounded beautiful, very sincere, and very, very quiet. The trend continued for the next three songs -- despite being very near the stage, the band's vocals seemed intentionally low, and the instrumentals weren't much better.

I'm hearing from others that the rest of their set killed, so I'll give them a benefit of the doubt -- but man, if only the volume had been cranked.

Kids these days. Volume was not at all an issue over at NERO's set at Perry's dance stage. This year, Perry's stage is topless, that is, it is no longer the "tent" it was once billed as. This was wise planning on the organizers' part because it allowed for the installation of video screens that looked incredibly impressive with Chicago's skyline in the background. (See photo below.) The dance party that ensued was, expectedly, wild.

Stabbing near the park. According to police, a 53-year-old male ticket reseller was stabbed almost directly outside of the festival. Police also say gatecrashing is happening Friday despite the festival's attempts to thwart the practice.

Hey, Rahm! It appears Chicago's mayor introduced The Black Keys. While wearing khaki cargo shorts. Pretty rad!

'I can't fucking hear you!' Meanwhile, I made my way back over to the festival's north end where Black Sabbath, Ozzy Osbourne and all, was making his presence very much known. Surprisingly, the crowd was incredibly sparse at the stage -- it had been far more crowded for Metric earlier in the day -- which says a lot about where the bulk of the ticketbuyers' priorities lie. That said, I savored getting a rare chance to watch Osbourne and company rock out and scream, "I can't fucking hear you!" at the crowd every 10 minutes while also playing some kick-ass rock.

Celebrity count? Unless you count checking out this tweet from Kelly Osbourne, no. Stayed clear of the afterparty scene Friday. At Filter magazine's Lollapalooza kickoff party Thursday evening at Logan Square Auditorium, Twin Shadow and Neon Indian headlined a raucous affair that offered up plenty of swag, booze -- sake and tequila! -- and more. But, alas, no celebrities that we saw.

Want to hear more about Lolla, day one? Our pals over at Spinner have some notes up from Friday as well. We noticed a lot of problematic co-opting of Native American attire too, Dan.

All photos below appear courtesy of Justin Barbin unless otherwise noted.

Check back on HuffPost Chicago for photos and reviews from Grant Park throughout the weekend. Watch parts of the event streaming live on the festival's YouTube channel. Follow @robojojo on the ground for real-time coverage as much as the festival's awful cell reception allows.

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  • Metric

    (Photo Joseph Erbentraut/The Huffington Post)

  • SBTRKT

    (Photo Joseph Erbentraut/The Huffington Post)

  • The Head and the Heart

  • The Head and the Heart

  • The Head and the Heart

  • The Head and the Heart

  • The Head and the Heart

  • The Head and the Heart

  • The Head and the Heart

  • The Head and the Heart

  • Yo-Landi Vi$$er, Ninja

    Yo-Landi Vi$$er, left, and Ninja of Die Antwoord perform at the Lollapalooza music festival on opening day in Chicago's Grant Park on Friday, Aug. 3, 2012. (Photo by Steve C. Mitchell/Invision/AP)

  • Yo-Landi Vi$$er, Ninja

    Yo-Landi Vi$$er, left, and Ninja of Die Antwoord perform at the Lollapalooza music festival on opening day in Chicago's Grant Park on Friday, Aug. 3, 2012. (Photo by Steve C. Mitchell/Invision/AP)

  • Band of Skulls

    (Photo Joseph Erbentraut/The Huffington Post)

  • Michael Angelakos

    Michael Angelakos of the electro-pop band Passion Pit performs at the Lollapalooza music festival on opening day in Chicago's Grant Park on Friday, Aug. 3, 2012. (Photo by Steve C. Mitchell/Invision/AP)

  • The Shins

  • The Shins

  • The Shins

  • The Shins

  • The Shins

  • The Shins

  • The Shins

  • The Shins

  • A flying pig in the audience before M83

    (Photo Joseph Erbentraut/The Huffington Post)

  • (Photo Joseph Erbentraut/The Huffington Post)

  • M83

  • M83

  • M83

  • M83

  • M83

  • NERO

    (Photo Joseph Erbentraut/The Huffington Post)

  • Ozzy Osbourne

    Ozzy Osborne of Black Sabbath performs at the Lollapalooza music festival on opening day in Chicago's Grant Park on Friday, Aug. 3, 2012. (Photo by Steve C. Mitchell/Invision/AP)

  • Ozzy Osbourne

    Ozzy Osbourne of Black Sabbath performs aLollapalooza on opening day in Chicago's Grant Park on Friday, Aug. 3, 2012. (Photo by Steve C. Mitchell/Invision/AP)

  • Rahm Emanuel introduces The Black Keys