CBS has made it a clean sweep of Thursdays during May, burying the competish last week with a boffo turnout for the two-hour season finale of “CSI” and keeping the heat on Fox for the month’s young-adults crown.

The veteran crime drama peaked at 9:30 with more than 35 million viewers and nearly doubled the conclusion of NBC’s “The Apprentice 3” in demos. “ER” won at 10 in key categories for the Peacock, but a weak showing by “Will & Grace” at 8 gave the net no chance to keep up with CBS.

The Eye enjoyed its strongest Thursday in adults 18-49 (9.4 rating/24 share) since February 2003 (90-minute “Survivor” and a 90-minute “CSI”), according to Nielsen.

Night’s result capped the Eye’s first Thursday victory for an entire May sweep in adults 18-49, 25-54 and 18-34 since the advent of Nielsen’s People Meters in 1987.

It was a good night overall for broadcast television, especially the 9:30 half-hour, where the six nets combined for 68% of the 18-49 television audience and 69% of the 25-54 crowd.

For all its big Thursday numbers, though, CBS remains a long shot to win May in 18-49. CBS remained ahead of Fox through Saturday (4.3 to 4.0), based on Nielsen prelims for the weekend, but Fox figures to post its two biggest nights of the month on Tuesday and Wednesday as “American Idol” wraps up its season.

In the sweep ending Wednesday, Daily Variety projects Fox to finish with a 4.5 rating to a 4.2 or 4.3 for CBS, with ABC a competitive third and NBC a distant fourth. CBS will win in both adults 25-54 and total viewers.

Looking at Thursday, the first two-hour episode of “CSI” — directed by Quentin Tarantino — scored a boffo 10.6 rating/28 share in 18-49 and 30.73 million viewers overall from 8 to 10. It peaked in the final half-hour with a 12.9/30 in the demo and 35.72 million.

Head-to-head, “CSI” easily handled the conclusion of NBC’s “The Apprentice 3” (6.3/15 in 18-49, 14.02m), nearly doubling the reality show in 18-49 (12.3 to 6.3).

This is the lowest-rated of the “Apprentice” finales, down 19% in 18-49 from December’s second edition (7.8/21), although it did built sharply on its lead-in from “Will & Grace” (3.5/10 in 18-49, 7.92m). “Will” was down a huge 65% from its one-hour season finale of a year ago, when it aired behind “Friends.”

At 10, Noah Wyle’s final seg as a regular on NBC’s “ER” (8.6/21 in 18-49, 18.76) lifted the drama to its best scores since Feb. 3, beating CBS’ “Without a Trace” (6.8/17, 21.43m) in key demos. “ER” was down 24% in 18-49 from its 2004 finale.

Fox was above average with the season finale of “The OC” (3.5/10 in 18-49, 7.63m), which tied “Will & Grace” in 18-49 and won big among 18-34 (4.4/14 vs. 3.3/10). And at 9, spec “American Idol: World’s Worst Auditions” (4.0/10, 9.09m) did fine.

ABC was a distant fourth but above average with the Pacers-Pistons NBA playoff game (2.3/6 in 18-49, 5.77).

There wasn’t much to crow about for the nets as the weekend began, with the six broadcasters netting a puny 37 share in 18-49 on Friday, and the Big Four totaling a 29 share on Saturday.

Of note Friday was a solid perf by ABC’s “Wonderful World of Disney” original telepic “The Muppets’ Wizard of Oz” (prelim 2.2/8 in 18-49, 7.6 million). It placed second from 8 to 10 in 18-49 and led its slot in adults 18-34 (2.0/8), teens (2.6/13) and kids (5.2/19), with the net’s best perf in the time period in these younger categories in more than two seasons.

At CBS, a weak showing for the “32nd Annual Daytime Emmy Awards” (prelim 2.2/7 in 18-49, 7.6 million) continued that kudocast’s downward ratings trajectory.

NBC won the night with a two-hour “Dateline” that featured a Dateline/Court TV crime report. It logged the timeslot’s best results in 11 weeks (prelim 2.7/10, 9.5 million).

Fox led Saturday with its regular lineup (prelim 2.2/8 in 18-49).