The broadcast nets set the bar even lower last week, accounting for just 21% of the young-adult audience during what’s traditionally the least-watched frame of the calendar year.

Sure, Fox was hot kicking off the week with “Hell’s Kitchen,” and “Big Brother” opened its eighth edition to solid numbers on CBS, but festivities on and around the Fourth of July holiday kept most Americans away from their television sets, and no single program averaged 10 million viewers. Despite the broadcast woes, though, no scripted cable telecast ranked among the week’s top 20 primetime programs in adults 18-49, as viewing levels were sapped across the board.

With the Independence Day holiday landing smack in the middle of the week, the summer’s two hottest shows took a rest. Fox’s “So You Think You Can Dance” sat on the bench Wednesday and Thursday, while NBC’s “America’s Got Talent” opted for a repeat on Tuesday.

Overall, according to same-day viewing estimates by Nielsen, Fox made it 22 straight weeks as the leader among adults 18-49 — the longest streak for any net in nine years — with a 1.8 rating/6 share in the demo. The other nets were tightly bunched, with CBS (1.6/5) followed by NBC (1.5/5), ABC (1.4/5) and Univision (1.3/4), while TNT (1.0/3) was the top cabler.

CBS moved to the sole lead in adults 25-54 (2.2/7) and won as usual in total viewers (6.3 million), while Fox ruled once again among the younger 12-34 set (1.6/7).

Fox’s first-place 18-49 finish was paced by Monday’s “Hell’s Kitchen” (3.9/11 in 18-49, 8.12 million viewers overall), easily the week’s No. 1 show in 18-49 and 25-54 (4.1/11).

Net also won Thursday in 18-49 with a pair of “Are You Smarter Than a 5th Grader?” repeats and excelled Sunday with an hour of “Family Guy” encores; the second seg, at 9:30, was the week’s No. 1 scripted program in 18-49 and younger demos (3.4/9 in 18-49, 6.28m).

At CBS, “Big Brother 8” narrowly led its Thursday premiere hour in key demos (2.7/9 in 18-49, 7.40m) and then placed second in its first Sunday airing this season (2.1/7 in 18-49, 5.85m); on both nights, the summer vet was in line with its perf of a year ago.

And a special 10 o’clock “CSI” repeat on Thursday (2.7/8 in 18-49, 9.42m) dominated its hour and stood as the week’s most-watched program.

NBC got pretty good mileage out of a repeat of “America’s Got Talent” on Tuesday (2.1/8 in 18-49, 6.75m) and then led the next night with its annual “Macy’s 4th of July Fireworks Spectacular” (2.2/8, 7.58m).

Its primetime coverage of the Live Earth concerts on Saturday settled for a fifth-place 0.9/3 in 18-49 and 2.75 million viewers overall. Nielsen estimates that 19 million Americans watched at least six minutes of the concerts throughout the day on the networks of NBC Universal. (Bravo, for example, reported its best Saturday ever with its live coverage from Giants Stadium in the Meadowlands, drawing 7.9 million unduplicated viewers during one point or another of its nearly 18 hours on air.)

ABC had a sluggish week, getting some of its best numbers Monday at 9 for a special original episode of “Extreme Makeover” (2.2/6 in 18-49, 6.03m) and also putting up credible numbers the next night with newsmag “Primetime: Family Secrets” (1.9/6 in 18-49, 5.71m).

And the CW is really struggling in its first summer season, at least outside wrestling’s “Friday Night Smackdown” (1.4/5 in 18-49, 4.20m), which won its time period in key demos. Next highest-rated show on the net was a 7:30 p.m. Sunday repeat of the canceled comedy “Reba” (0.8/3 in 18-49, 2.07m).

TNT’s first-place cable finish was highlighted by Saturday’s NASCAR Pepsi 400 race (2.3/9 in 18-49, 6.16m), which won the night; Sunday’s airing of “The Bourne Supremacy” (1.5/4, 4.41m); and Monday drama “The Closer” (1.7/5, 7.19m).

Other top-10 scripted 18-49 finishers included USA’s Thursday spy drama “Burn Notice” (1.4/4 in 18-49, 3.94m), which saw potent week-two results, and Lifetime’s “Army Wives” (1.3/4, 3.55m), which continued to draw solid numbers.

On the nonscripted side, VH1’s “Charm School” looked pretty on Sunday (1.6/4 in 18-49, 3.59m), while History Channel scored on the same night with “Ice Road Truckers” (1.3/4, 3.13m).

ABC Family tapped into “Harry Potter” mania for its strongest week of the year. Weekend runs of “Sorcerer’s Stone,” “Chamber of Secrets” and “Prisoner of Azkaban” lifted the net to a top five weekly finish among cable nets in adults 18-49, 25-54 and total viewers (1.63 million).