Weather conditions have conspired to create the "perfect storm" for this year's mosquito season.

Cameron Webb, a medical entomologist at the University of Sydney, said a warm spring, a wet start to summer and tidal flooding of coastal wetlands had created perfect breeding conditions for mosquitoes.

Wet weather has prompted an early start to the mosquito season. Credit:Nick Moir

"All that's combined to mean that we've got a tonne of mosquitoes that are coming out not only of our wetlands, but also the suburbs as well," he told Fairfax Radio 3AW on Wednesday.

Dr Webb said the conditions had prompted an early start to the mosquito season, as well as an increase in the mosquito population.