“Jazz Fest is our bread and butter,” “Big Sam” Williams said. “Back in the day, it used to help some cats get through the entire year.”

Jazz Fest has become a time of year as much as an event at the Fair Grounds, and it is both crucial and stressful for many New Orleans musicians. But for Big Sam, Jazz Fest almost didn’t happen at all this year.

He was scheduled to play April 25 on the Acura Stage, but the monsoon-like afternoon rain forced organizers to cancel his show.

“We were the only stage not to go on because the wind was hitting us so hard it was blowing drums off the stage,” Williams said. “Crew members were being lifted up a little bit. The backdrop started falling. At least 10 crew members grabbed it so it didn’t come down completely.” He hoped he could get some time in, but by the time the front blew through, it was too late.

His show was the only one canceled because of the storm.

When Taj Mahal had to bow out of his set on the festival’s Fais-Do-Do Stage on May 2 because of illness, Big Sam’s Funky Nation got a second chance and stepped in. The stage is generally reserved for folk and Americana music, but Williams responded with a powerful blend of rock and funk made for the dance floor — just not the Cajun kind.

For Williams, the importance of Jazz Fest can’t be overstated.

“Jazz Fest is everything,” he said. “You get the maximum exposure right there in your own city. Every time you play something as big as the Acura Stage, you gain thousands of new fans.”

It’s also work, though, and it goes far beyond an hour or so at the Fair Grounds. Big Sam’s Funky Nation played four shows, and Williams performed at least three times a day. That’s good for business but tough on a personal life. Spouses and significant others understand, but it takes a toll anyway when the musician’s day doesn’t end until the sun comes up — a common phenomenon during Jazz Fest, when many clubs have late-night shows. “The Monday after Jazz Fest, I played a funeral,” he said.

His schedule remained so hectic after the festival that he had to schedule a birthday lunch with his wife and time with his little sister, who graduated this week, around a funeral, a gig and a recording session.

“Then Thursday morning, I left town,” he said. “It’s crazy, but I’m used to it now.”

For Big Sam’s Funky Nation and many New Orleans bands, Jazz Fest is also the start of a summer of touring, playing club dates and festivals around the world.

The festival helps pave the way for those shows as it introduces audience members from out of town to his music. When he visits their cities, he goes with an audience that at least partly knows who he is. “When you line your tour up, that’s another hundred people coming to your shows, spreading the word about you.”

Williams first made a name for himself as a trombone player with the Dirty Dozen Brass Band for four years, and he played with Allen Toussaint and Elvis Costello for two years after the release of their “The River in Reverse” album in 2006. Williams started Big Sam’s Funky Nation during that time, but he had to fit gigs around his other commitments.

It’s a tribute to Williams’ sound and charisma that the group thrived, but eventually post-Hurricane Katrina New Orleans caught up to him. He let go of his other jobs in 2007 and went full-time with Big Sam’s Funky Nation, but he had to go to Florida to find a band that could be full-time with him.

The Florida musicians made it possible for him to play, but they struggled to get the funk/rock balance right.

“They were all good musicians, but no matter how much I rehearsed them, it was more complicated than I thought it would be,” Williams said.

The band slowly went through lineup changes, evolving and swapping New Orleans musicians back into the mix until in 2009 or 2010 it became what he had been looking for.

Now when he plays Jazz Fest and festivals like it, he knows he’s often introducing people to his music, whether it’s because they haven’t heard what he’s been up to recently, or in some cases they’ve never heard him.

“Believe it or not, we’ll have people who’ll say, ‘We’re huge New Orleans fans’ and they’d talk about Allen Toussaint and Dr. John, Rebirth and the Dirty Dozen, then they’ll say they’ve never heard of Big Sam’s Funky Nation,” Williams said, partly amused, partly wounded.

“But it is what it is. People don’t get to see all of the artists. And you’d be surprised. There are people who don’t know who Beyoncé is.”