A welcome surprise during broadcast’s usually dry summer months: CBS’ Under the Dome just debuted to a whopping 13.1 million viewers and 3.2 rating among adults 18-49 last night.

That’s the most-watched summer debut on any network since NBC’s The Singing Bee in 2007. It’s also very competitive with last season’s crop of dramas, matching Fox’s The Following as the second-highest new drama debut (NBC’s Revolution was #1).

Under the Dome is based on the Stephen King novel and was originally developed for CBS’ corporate cousin Showtime. The ratings make you wonder: Should CBS have aired Dome during the regular season? After all, it just pulled a bigger number than Vegas or Golden Boy. Maybe. But I like that CBS went big with a heavily promoted major scripted show during the so-called off-season. When broadcasters air scripted shows in the summer, it’s often weak filler (like NBC’s recent Crossing Lines debut). Shows that are inexpensively acquired, softly promoted. Low expectations theater. It’s an echo of when broadcast networks used to largely disregard summer all together, filling it with repeats, until cable networks came along and started mining the sunny months with original programming. Nowadays, you have to put on your best content all the time, there’s simply too many other decent distraction choices out there to get away with something that isn’t demanding the viewer’s attention.

Under the Dome also continued the apocalyptic-TV winning streak: AMC’s The Walking Dead, Revolution and now Dome — which isn’t about the end of the whole world, obviously, but tells an apocalypse story on a small-town scale.

What did you think of Under the Dome? Will its numbers hold up in the weeks to come? Check out EW’s recap.