Mel B

Mel B on the New Jersey auditions red carpet for America's Got Talent on March 2, 2015.

Eric Liebowitz/NBC

Memorial Day isn't the only sign of summer. The return of America's Got Talent to television screens, along with a liberal dose of reality shows and reruns, are just as reliable as thermometers.

NBC was last week's most popular television network for the first week since it televised the Super Bowl, helped primarily by America's Got Talent. The popular summer show was the only one to register more than 10 million viewers last week on the night it was broadcast.

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The Nielsen company's list of top 20 programs last week also included three prime-time newsmagazines besides 60 Minutes

The news shows provide relatively cheap programming for networks looking to cut costs in the slow summer months.

As for breezy diversions, CBS' The Briefcase was the week's most popular reality show, while NBC's American Ninja Warrior and I Can Do That both scored well among younger viewers.

NBC's well-publicized summer series Aquarius landed in the top 20, but the 1960s-themed show attracted an older audience, which is not a plus in the TV business.

NBC averaged 5.5 million viewers for the week and easily won among the 18-to-49-year-old demographic it targets. CBS averaged 5.4 million, ABC had 3.9 million, Fox had 2.7 million, Univision had 2.2 million, Telemundo had 1.4 million, ION Television had 1.2 million and the CW had 1 million.

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ESPN was the week's most popular cable network behind its coverage of the Golden State-Houston NBA playoff series. The sports network averaged 2.5 million viewers in prime time, History had 1.89 million, USA had 1.76 million, the Disney Channel had 1.72 million and HGTV had 1.59 million.

The evening newscast ratings race was extremely tight, with NBC's Nightly News averaging 7.68 million viewers and ABC's World News Tonight having 7.65 million. The CBS Evening News had 6.4 million.