Under the Dome – First Look Video

CBS appears to have found a legitimate summertime hit in its adaptation of the Stephen King novel “Under the Dome,” whose first episode drew an audience of more than 13 million Monday night

In preliminary overnight ratings, the show’s audience reached 13.1 million, a number likely to grow, especially when delayed viewing is included.

The premiere of “Dome,” a 13-part mini-series set in a small town that is suddenly sealed off by a mysterious clear dome, also scored with the audience that counts for many advertisers — viewers between the ages of 18 and 49 — where it registered a 3.2 rating. That would count as a hit rating any time of year; in the summer, when networks have a hard time eclipsing a 1 rating in that category, the numbers for “Dome” represent a breakout performance.

On Monday night, the show faced the final game of an exciting N.H.L. championship series, which could mean a large number of hockey fans recorded the show to watch later. Also, with largely positive reviews, “Dome” has the potential to build on its ratings in future episodes.