RATS are being forced above ground into homes and restaurants as city sewers fill up with rainwater.
Pest controllers in Brighton and Hove have reported an increase in calls about the rodents over the last few months, which have been some of the wettest on record.
Experts say the lack of a harsh winter in recent years had helped the rodent population to soar.
And the heavy downpours that have led to flooding in recent months have sent rats scurrying for higher ground – and into people’s homes.
One local Pest Control contractor said he was receiving around five calls a week about rats, almost twice as many as last year.
He said: “The rain hasn’t dampened the rodent’s spirits. They’re thriving.
“The fact that we have had no harsh winters recently is a contributing factor as there is no death rate in these rats and they can reproduce quickly and recent heavy rainfall had filled sewers up, pushing the rats out of drains and into buildings in search of food.
He said: “Compared to last year I’ve seen an increase in the amount of Rodenticide I have had to buy. I have been through one 20kg sack in a month and that is a lot for me.
A Brighton and Hove council spokeswoman said: “We have not seen a significant rise in requests for treatment this year.
“We do not believe the recent humid weather has lead to an increase of rat sightings, however, extreme wet weather conditions can lead to overflow from storm drains, causing rats to be displaced, but this is quite unusual.“