The Long Beach Fire Department responded to the fire on the beach near 12th Place just after midnight.
The department says LGBTQ members of the Marine Safety Division painted the tower during Pride month last year and it has since "served as a symbol of our strong support for the diversity within our ranks & community."
The LBFD also says the tower will be replaced and repainted by lifeguards.
Though the cause of the fire is still under investigation, Mayor Robert Garcia tweeted that he personally has "little doubt this was an act of hate."
"To whoever committed this act, we will rebuild it better and brighter," Garcia also said in his tweet.
City News Service contributed to this report.