West Nile is on the decline in Illinois, according to public health officials.

The Illinois Department of Public Health said there’s been a slight decrease in the percentage of mosquito samples testing positive for the West Nile virus in August. 

Officials attribute the decrease to slightly cooler temperatures, and stormy weather this weekend may continue the trend – but only for so long.

The department’s Linn Haramis said heavy rains could wash away mosquito larvae growing in standing water.

“In the short-run it’ll actually suppress West Nile virus activity. But then if we go back to a period of high temperatures after that, two or three weeks later you’ll start to see an increase,” he said.

Illinois currently has 56 confirmed cases of people infected with the West Nile virus. Haramis expects more cases will be reported now through the first frost of the year. 

The total number cases reported last year was 34.