Allegedly four seasons exist in the world — we hear they are called summer, fall, winter and spring — but in Vegas such distinctions do not exist. Here, only one season reigns supreme: Pool Season, the time of sun, skimpy bikinis and the sweet sounds of poolside concerts.

Hard Rock Hotel & Casino has announced the return of Friday Night Live, its poolside music series, for a fourth season. Kicking off the series May 7 is Flyleaf, the platinum-selling rockers best known for songs like “All Around Me” and “I’m So Sick.” De La Soul, Rusted Root, Gin Blossoms, Pepper, The Original Wailers, Los Lonely Boys and Toots and the Maytals are scheduled for subsequent Friday performances, with others to be announced later.

The Friday night performances are the perfect start to those simmering summer weekends, especially those that end with Rehab, the Hard Rock Hotel’s Sunday pool party. (Those devious daytime parties begin again in April.)

Tickets for Friday Night Live are around $25 each (plus fees) and go on sale at noon Saturday.

Friday Night Live schedule

• Flyleaf. May 7, 7 p.m. $25.

• Toots and the Maytals. May 14, 8 p.m. $28.50

• De La Soul. May 21, 9 p.m. $24.50.

• Rusted Root. May 28, 9 p.m. $27.50.

• Gin Blossoms. June 4, 9 p.m. $25.

• Pepper. June 11, 9 p.m. $25.

• The Original Wailers. June 18, 9 p.m. $24.50.

• Los Lonely Boys. August 13, 9 p.m. $25.