Maybe this summer, cable is not going to own prime-time television.

Borrowing heavily from the cable playbook, CBS has set out to reverse the trend toward ever-dwindling network ratings — and intense attention directed toward cable dramas — in the summer. In its new series, “Under the Dome,” CBS may have done it.

The opening ratings for “Dome” last Monday qualified as spectacular: more than 13.5 million viewers for the premiere, the biggest audience for a summer drama in more than 20 years. The show added more than three million more viewers when three days of delayed viewing was counted, CBS announced Saturday.

Maintaining numbers like that could mean significant profits for CBS, which created a can’t-miss formula for financing the show that included a presale of the episodes for streaming on Amazon Prime, and now may expect a surge in spending from advertisers looking to reach summer consumers at the same time.

Even more important, CBS’s executives are so encouraged by the early ratings results that they foresee the potential “to create a whole new model for summer programming” said David F. Poltrack, the network’s chief research executive.