Falling Skies has been a surprise hit on TNT, a fact that’s become even more apparent as the numbers for the feature-length finale have come in. The two-hour episode netted 5.6 million viewers, according to a press release from the network.

That makes the finale the most-watched episode since the premiere on June 19th, which scored slightly better at 5.9 million viewers (and a full 8 million in the Live +7 ratings). Falling Skies has averaged 4.8 million viewers across the 10-episode freshman season, numbers to make any cable show (and many broadcast shows) jealous. About 50% of viewers are watching on DVR devices, so the finale’s ratings should increase significantly when the +7 ratings come in two weeks.

The genre show is also performing surprisingly well in the all-important 18-49 demographic: 2.5 million viewers of Sunday night’s finale fell in the range. With that, Falling Skies is the best-performing new basic cable show this year. TNT renewed the show after its fourth episode, and Season 2 is currently scheduled for another 10-episode run next summer.

The show’s success is even more surprising given its unashamedly sci-fi premise. Science fiction shows have been falling left and right for the last year: No Ordinary Family, V, The Event, Caprica, Stargate Universe it’s refreshing to see a genre show get a good jump out of the gate.

Audience reactions to Falling Skies have been mostly positive, with critical reactions to match. If for no other reason, a good chunk of the viewership will probably return next year just to find out what happened after the impressive finale cliffhanger.

Falling Skies is also making a splash on international television. According to TNT, the show is the best-performing launch ever for parent company Turner in Spain, Germany and Austria, with strong performances in the UK,  Australia and Germany. The series launched almost simultaneously in over a hundred markets.

Falling Skies is scheduled to return to TNT in the summer of 2012.

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