We all scream for ice cream, especially when the frozen treat is free or cheap.

Sunday is National Ice Cream Day and restaurants across the nation are celebrating with discounted desserts.

The day became official 34 years ago when President Ronald Reagan declared the third Sunday of July as National Ice Cream Day and the month of July as National Ice Cream Month.

Back in 1984, Reagan’s proclamation noted the ice cream industry generated $3.5 billion in annual sales.

According to Womply, a small business software provider, July is the No. 1 sales month of the year for the ice cream and frozen yogurt businesses, said Brad Plothow, the company’s vice president of brand and communications.

“The data confirm that as the summer heats up, people chill out with an ice cream in droves,” Plothow said.

But what’s the biggest day for ice cream sales at local shops?

Plothow said last year “the Friday before the confection-fest was the third-best revenue day of the entire year for ice cream and frozen yogurt businesses from coast to coast.”