Two teenagers have been hospitalised with stings by deadly irukandji jellyfish in waters off Fraser Island in southeast Queensland.

The boy, 13, and girl, 14, were airlifted to Hervey Bay hospital on Friday afternoon after paramedics were called to their boat off the island's western coast.

Two other people in their group with suspected stings were treated at the scene.

The irukandji jellyfish. (AAP)

They have since been released from hospital.

Yesterday a warning was issued of the risk of a spate of irukandji jellyfish stings as the weather changed in Queensland.

One of the world's deadliest creatures, the jellyfish prefer calm, warm waters and tend to avoid areas with heavy rainfall. Some far north areas of the state have received up to 200mm since Boxing Day.

But the risk of irukandji stings will increase once the rain stops, according to toxicologist Jamie Seymour.

"All this rain, it'll fire all jellyfish up," Professor Seymour said.

"What you tend to find is after you've had big rainfall events, like we're having at the moment, we'll have large numbers of jellyfish, assuming the weather settles back down.

A sting from the tiny Irukandji jellyfish can be deadly. (AAP)

"If we don't get rain, we get very small numbers of irukandji."

Prof Seymour said Queensland had recorded almost 20 irukandji stings this year, including four off Fraser Island.

Those figures do not include the stings recorded yesterday.

"It is above average. In Cairns, we've had at least seven stings. This time last year, we had one," he said.

"The (stinging) season has become longer. 50 years ago, the season was about a month.

"Now, it's about 5-6 months.

"It correlates quite nicely with increasing water temperature."