CHICAGO – Lollapalooza and the Austin City Limits festival are a tale of two siblings.

Both are run by one parent company: Austin-based C3. And both draw about 200,000 fans to a huge city park where more than 100 bands play on eight stages.

But like many siblings, one's got a lot more going on than the other.

ACL, which takes place Sept. 26-28, is the problem child. With temperatures that routinely flirt with the 100-degree mark, it's less a festival than a test of human survival.

Lolla, which ended three sold-out days Sunday, is the kid with the bright future. Launched in '91 as a touring festival, it's been based since 2005 at Chicago's lakefront Grant Park, a milelong site filled with thousands of trees and gardens and the landmark Buckingham Fountain.

"Your eyes are full of nature, yet you're in the middle of Gotham with the most gorgeous architecture up in the skyline," says founder Perry Farrell, who licenses the name to C3 but remains the face of the festival.

"Nothing beats this setting," says 38-year-old Tom Corcoran, a New Mexico festival junkie who's been to every ACL and Lollapalooza. "If you're comparing the two, Chicago beats ACL easily."

But it's not just the scenery that sets Lolla apart. It's the logistics.

Its downtown location makes it easy for fans to drive to the fest or take a train – options that don't exist at ACL in Zilker Park, which is infamous for its hourlong waits for shuttle buses and taxis. At Lollapalooza, many out-of-towners simply walk to the park from their hotels.

"We're staying a few blocks away, so we can come and go anytime we like," says 44-year-old Shawn Monty of New Hampshire, who came with his wife and teenage son.

Sound-clash problems are standard at multistage festivals, but they're not nearly as bad at Lolla as at ACL, where bands on the two big stages often drown out each other.

"Sound's a little tougher in Austin because of the circular nature of the park," says C3 promoter Charlie Walker. "But the walk here is much longer because it's a long, skinny park."

True, it takes at least 20 minutes to trek between Lolla's two main stages. But the journey through Grant Park is a pleasant one. There are groves of trees everywhere (one has dozens of free hammocks), and four of the smaller stages are set in the shade. Families camped out on blankets under trees were a common sight during the weekend.

FILE/Austin American-Statesman

Thousands braved the Texas heat to watch Death Cab for Cutie at 2005's Austin City Limits festival in Zilker Park.

Not counting the shade factor, the big difference between the fests is the temperature. With a constant lake breeze, Lollapalooza stayed mostly in the 70s and low 80s. The weekend high was 86; the normal August high is 81.

At ACL, the mercury routinely hits the mid- to high 90s, with a high of 108 in 2005. It's not only the most uncomfortable rock festival in the U.S., it's potentially dangerous in terms of the weather, with medics treating hundreds of people for heat-related illnesses every year.

Mr. Farrell says "80s is about the limit" for festival comfort. "I don't like it when it gets in the 90s. Then you need tents."

Not everyone agrees. All of his friends complain about the heat at ACL, says Mr. Corcoran, the festivalgoer from New Mexico, "but I'm one of those guys who can stand in the sun with no shirt and not be affected."

Mr. Walker concurs, saying, "Texans are acclimated to extreme heat." ACL is in September, he says, because cooler parts of the year tend to be wetter and less likely to draw huge crowds and big-name bands.

No matter what the thermometer reads, both festivals have become hugely profitable. Lolla sold out for the first time this year, with 225,000 people attending over three days. With seven weeks to go, ACL is already close to selling out.

"I'm bullish on the future of both festivals," says Mr. Walker.

Apparently, if you stage it, they will come, no matter what the climate.

But until ACL moves to a cooler month, it'll never be in the same league as a world-class festival like Lollapalooza.Plan your life

This year's Austin City Limits Music Festival is Sept. 26-28 at Zilker Park in Austin. Three-day passes are sold out, but single-day and VIP passes are still available. www.aclfestival.com.

FIRST YEAR

Austin City Limits: 2002

Lollapalooza: 2005 (based in Chicago)

NUMBER OF 2008 ACTS

ACL: 130

Lolla: 139

2008 HEADLINERS

ACL: Foo Fighters, Beck, Robert Plant & Alison Krauss

Lolla: Radiohead, Rage Against the Machine, Kanye West

AVERAGE DAILY HIGH TEMPERATURE

ACL: 90 degrees

Lolla: 81 degrees

3-DAY REGULAR PRICE

ACL: $170

Lolla: $205

2007 ATTENDANCE

ACL: 200,000

Lolla: 167,000

2007 GROSS

ACL: $11.3 million

Lolla: $9.8 million