Swimmers and surfers: Beware. The monthly influx of box jellyfish is expected to start tomorrow.

The most commonly affected area is Waikiki Beach, especially on the 'ewa end of the Kapahulu groin.

Other near-shore waters that may see box jellyfish include Hanauma Bay, Poka'i Bay, Makaha Surfing Beach and Waimea Bay.

Those stung by box jellyfish are advised to flush the area with copious amounts of white vinegar.

Anyone who is stung and experiences difficulty breathing, muscle cramps or spasms or persistent pain should seek immediately medical attention.