Memorial Day weekend's worst performance in 18 years at the box office has caused the prices of movie theater companies' stocks to slide.

The weekend is just one part of the movie industry's poor performance this summer. Revenue is down 4.7% compared with last year's gross during the same time period.

Pirates of the Caribbean: Dead Men Tell No Tales, the fifth installment of Disney's (DIS) - Get ReportPirates franchise,led the box office, bringing in $78.5 million. That, however, was shy of the $90.2 million the fourth movie in the series, Pirates of the Caribbean: On Stranger Tides, garnered in its three-day opening weekend in May 2011.

Paramount Studios' Baywatch, meanwhile, flopped in theaters with a long weekend gross of $23.1 million.

If the summer season continues like how it opened, these film exhibitors may feel the heat.