Update: The sizable drop “Under the Dome” endured in the overnight household ratings extended to the fast national data.

Monday’s second season premiere of “Under the Dome” posted a 2.2 adults 18-49 rating with 9.4 million viewers. The numbers were down 33% and 30%, respectively, from those delivered by last year’s series premiere.

The episode drew a 1.1 in the men 18-34 demographic.

The numbers remain strong by summer broadcast standards but obviously lessen the extent to which “Under the Dome” can drop without trading away its status as a hit as the season progresses.

While it scored the night’s largest household overnight audience and performed very well by summer broadcast standards, the second season premiere of “Under the Dome” endured a significant ratings decline.

Monday’s episode delivered a 5.9 household rating in the overnight metered markets, which represented a decline of 36% from the series premiere’s 9.2.

Last year’s episode ended up drawing a 3.3 adults 18-49 rating with 13.5 million viewers. So strong was the premiere performance that even as the show began declining in the ratings, it remained an unequivocal summer hit for CBS in 2013.

Even if the season two premiere also suffers the aforementioned 36% decline in adults 18-49 and total viewers, its performance would still be a solid one for a summer series.

Such a drop would, however, remove some of the show’s leeway for falling as the curiosity and buzz surrounding the season premiere fade.