NEW ORLEANS — Friday was a muddy, overcast, unusually cool and windy day at the New Orleans Jazz & Heritage Festival.

For festival-goers, boots and a light coat were a good idea. But with so much mud on the Fair Grounds Race Course infield, many festival-goers walked around in sandals or bare feet.

The inhospitable weather didn’t stop the music. Nor did it prevent legions of people from showing up for the second of Jazz Fest 2013’s final four days.

The day’s big pop act, Maroon 5, drew a vast crowd of the size that usually attends performances by Jazz Fest headliners at the Acura Stage.

“What an honor it is to be here tonight with you guys!” front man Adam Levine told an audience of young and many not-so-young people, all of whom, no matter their age, sang along with Maroon 5’s many hits.

Levine and Maroon 5 included an excerpt from Michael Jackson’s “Don’t Stop ‘Til You Get Enough” in their show. Jackson’s influence, heard in Levine’s falsetto singing and the band’s pop-rock-rhythm-and-blues sound, couldn’t be missed.

While it’s usually a challenge for Jazz Fest-goers to decide which acts to see on any given day, it was Levine who noted the world-class acts who were appearing at the same time as Maroon 5. He mentioned 80-year-old country legend Willie Nelson, at the Gentilly Stage, and reggae pioneer Jimmy Cliff, who entertained an expansive, hand-waving crowd at the Congo Square Stage.

Earlier in the day, the Mavericks, a band from Miami that rose to stardom from Nashville as a country act, didn’t let the weather slow them down. As singer Raul Malo told his Gentilly Stage audience, “we’ve dreamt our whole lives of coming here. We don’t care if it’s rainy and muddy!”

Sending an infectious blend of Latin, boogie-woogie and honky-tonk rhythms from the stage, not to mention wailing tenor sax and Tex-Mex accordion solos, the group produced enough musical heat to warm their clearly delighted audience.

During the especially Latin “Dance in the Moonlight,” people danced in the mud, finding it a great way to warm up. Another Latin-bent song, “Come Unto Me,” featuring its cool vintage sound and heavy, recurring guitar riff played by Eddie Perez, belongs in a Quentin Tarantino movie soundtrack.

There was much warmth, too, in the filled-to-capacity Gospel Tent when Irma Thomas sang her tribute to New Orleans-born gospel great Mahalia Jackson. Thomas, prior to her secular career in rhythm-and-blues, grew up singing gospel at Home Mission Baptist Church in New Orleans’ Zion City neighborhood.

After singing “He’s Got the Whole World in His Hands” in her rich alto tones, Thomas, one of the hundreds of thousands of Gulf Coast residents who lost a home to Hurricane Katrina and the flooding in New Orleans, offered an expression of her faith.

“I know he’s got our city in his hands because we have been in many, many storms and we’re still here,” she said.

Holly Williams, 32, the daughter of Hank Williams Jr., performed her early afternoon show at the Gentilly Stage for an audience that started out small but quickly grew. Reed-slim like her grandfather, Hank Williams Sr., she follows family tradition by writing her own songs and accompanying herself with acoustic guitar.

Playing with a band that included her guitar-playing, co-writing husband, Chris Coleman, Williams performed often emotional material.

Many songwriters have written about the loneliness of being on the road, missing home and loved ones, but Williams put a new spin on the traveling musician’s life. In “The Highway,” she sings about being stuck at home and missing the road and seeing a new city every day.

“Roll with me, roll with me,” Williams pleaded in song. “Down to New Orleans.”

Williams turned the emotion up and showed her gift for storytelling in “Waiting on June.” Her late maternal grandparents, with whom she spent summers with in north Louisiana, inspired it. The June in the song is a reference to her grandmother and the lyrics are sung from the loving perspective of her grandfather.

For her final song, Williams turned to a country classic she didn’t write.

“I always feel like I gotta do a family song,” she said, meaning a Williams family song. There are so many great songs among those, she added, it’s difficult to pick just one. In the city of good times, she chose her grandfather’s country-gospel classic of spiritual salvation, “I Saw the Light.”

Festival officials delayed the first performances of the day Friday at the Fair Grounds’ 11 stages slightly, pushing them to noon. Groundskeepers used the extra time to prep the soggy site. The day’s early music sets were shortened and, by about 1:30 p.m., performance times were back on schedule.

Jazz Fest continues through Sunday.