North Queensland rain to raise deadly jellyfish irukandji threat

Irukandji jellyfish may be elusive during far north Queensland's big wet but they're set to come back in big numbers when the sun comes out.

After they forced the closure of two northern Queensland beaches last weekend, including Ellis Beach near Cairns when a teenage girl was hospitalised with stings to her upper body, no irukandji have been spotted in swimming areas since.

One of the world's deadliest creatures, the jellyfish prefer calm, warm waters and tend to stay away during heavy rainfall, with some far north areas receiving 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 told AAP.

"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.

"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.

"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."