More than 75,000 endured days that frequently topped 100 on the heat index. Heavy rain fell when the festival gates opened on Wednesday night, muddying the grounds. Bodies splayed out in exhaustion across the grass were common, as were umbrellas to shield the sun.
"How do you do it?" marveled singer-songwriter Regina Spektor just one number into her Sunday afternoon set. "You guys are like heat superheroes."
And yet, with few exceptions, the crowd remained enthused, eagerly soaking up some 100 acts, traipsing from stage to stage to seek out an unforgettable moment at the Bonnaroo Music & Arts Festival.
The Saturday evening double bill of headliner Jay-Z and Stevie Wonder was the apex. Both performed acts of incredible individual showmanship: flawless swagger and bombast from Jay-Z; warm, humanistic sing-a-longs from Wonder.
Introducing Wonder, Conan O'Brien shouted to the crowd: "All the mud, all the rain, all the heat - it's all worth it."
O'Brien was the most omnipresent figure at this year's Bonnaroo. The comedian twice performed his "Legally Prohibited From Being Funny on Television" show, and he played master of ceremonies on the main stage Friday and Saturday.
"In six months, I've gone from hosting `The Tonight Show' to performing at a refugee camp," O'Brien, who begins a new show for TBS in November, said Friday.
Comedians taking music seriously (to a degree) was a theme. Bonnaroo, one of the nation's largest festivals, has for years added comedians to the bill, having them perform in a circus-like tent.
Aziz Ansari, J.B. Smoove, Margaret Cho and Jeffrey Ross were among those, but Steve Martin (with his bluegrass band the Steep Canyon Rangers) and Jack Black (with Tenacious D) were out on the music stages.
"Hope you had your breakfast," Martin deadpanned to his evening audience.
As though living out a boyhood dream, O'Brien - a capable guitarist - played rock star through the weekend. His performances included joking versions of songs by Elvis and Willy Nelson, but also an earnest encore of the Band's "The Weight," in which he left the stage to shake hands with - and be mobbed by - the crowd.
On Thursday night, when Bonnaroo was warming up with a handful of acts, O'Brien even played a set of rockabilly at Jack White's Nashville label, Third Man Records. White, whose current band, the Dead Weather, played Saturday, recorded O'Brien's performance and will release it.
Perhaps no one made more effort to get to Bonnaroo than the rapper Kid Cudi, who began Friday in a New York jail cell, arrested for criminal mischief and criminal possession of a controlled substance. He still made his scheduled 2 a.m. performance Saturday, grinning as he took the stage: "I really wanted to be here tonight."
Of course, not everyone drinks the Kool-aid.
"We're really into festivals," Dan Auerbach of the Black Keys said sarcastically in an interview. "Cheese fries and 120 degree heat, port-a-johns."
"It's hard to play during the day," echoed Auerbach's bandmate, Patrick Carney. "Everyone's standing out in 90-degree heat, there's no lights, there's no atmosphere, you really don't have any control over the show. ... It's actually to the point right now where, I think, we're probably going to start passing on festival offers."
The heat led to cases of dehydration, though Ashley Capps, festival co-founder and president of festival co-producer AC Entertainment, said, "For the most part, everyone stayed healthy." Coffee County Sheriff Steve Graves said arrests were up slightly with more than 50 as of Sunday afternoon, but that festival-related crime was "about normal."
Increasingly, fans can skip the traffic, mud and heat and experience a piece of it online. Many performances were webcast live on YouTube and on NPR.org. The Bonnaroo channel on YouTube drew more than 1.1 million views.
Bonnaroo began as primarily a jam-band event, but has grown far beyond those roots, as evidenced by the eclectic lineup. Southern rock band Kings of Leon headlined the main stage on Friday, a day that also included performances by LCD Soundsystem, the National, She & Him and Tori Amos.
Weezer, Jimmy Cliff, Jeff Beck and Ozomatli were among those who played Saturday. Headliner Dave Matthews Band was to close out the festival Sunday evening, after sets by John Fogerty, Phoenix, Against Me! and many others.
Whether a festival like Bonnaroo resonates is predicated on what one puts into it, said Wayne Coyne, the lead singer of the Flaming Lips. The band performed a fuzzy, psychedelic version of Pink Floyd's "Dark Side of the Moon" on Saturday.
"The magic is really in your mind," said Coyne. "It's not going to be the greatest show ever - your life isn't going to be the greatest show ever. But if you try to make it the greatest show ever, it might be."