Atlantic City casino revenue dropped 13 percent in June, compared to the same time a year ago. Each of the 12 casinos posted a revenue decrease last month.

Atlantic City skyline (Jerry Driendl, Getty Images)

The casinos took in $240.2 million, and according to The Associated Press, the struggling resort town is on pace to bring in less than $3 billion from gamblers for the first time since 1991.

Roger Gros, publisher with Global Gaming Business, placed a lot of the blame on the weather.

"Every weekend was pretty bad in June, and that's a killer for Atlantic City," he said.

Rain fell on 15 of June's 30 days.

May has been the only month this year in which Atlantic City casinos posted less than a double digit decline.

Gros also noted that June 2013 had one less weekend day than June 2012. He expressed  confidence that Atlantic City's July numbers will be much better, thanks to the long July 4th weekend.