Facing “American Idol” may be tougher than recovering from a nuclear holocaust for the residents of “Jericho.” The CBS post-nuclear disaster drama, which returned to the Wednesday 8 p.m. timeslot last night after a three-month hiatus, saw big declines from its fall average.

“Jericho” averaged a 2.4 adults 18-49 rating, according to Nielsen overnights, down 27 percent from its 3.3 average last fall.

Of course “Jericho” was far from the only show to suffer in the path of “Idol.” ABC’s comedies and NBC’s “Friday Night Lights” all fell to or neared season lows as the Fox reality show aired the second of three two-hour episodes this week. It usually airs at 9 p.m. on Wednesday.

“Jericho” did place second in the timeslot behind “Idol’s” 11.3 18-49 average, and it also took second in total viewers.

It will be more telling when Fox’s usual Wednesday 8 p.m. occupant, “Bones,” returns to the schedule whether “Jericho” has really lost some of its fall audience or whether they’re just checking out temporarily to catch “Idol.”

The show was a nice surprise for CBS last fall, earning the network’s first full-season pickup, and it looked so much the stronger alongside the network’s other disappointing dramas, such as “Smith” and “3 Lbs.,” that were quickly canceled.

Meanwhile, Fox was first for the night among 18-49s with a 12.2 average rating and a 31 share. CBS followed at 3.5/9, with ABC third at 3.3/8, NBC fourth at 2.1/5, Univision fifth at 1.6/4 and CW sixth at 1.4/4.
 
Fox led each of its two hours rather easily, starting with an 11.3 rating at 8 p.m. for the first hour of “American Idol.” CBS was second with a 2.4 for “Jericho,” while ABC and Univision tied for third at 1.9, ABC for “George Lopez” (2.2) and “Knights of Prosperity” (1.6) and Univision for “La Fea Mas Bella.” That left NBC fifth with a 1.8 for “Friday Night Lights” and CW sixth with a 1.3 for a “Beauty and the Geek” reunion show.
 
At 9 p.m. Fox led again with a 13.2 for the second half of “Idol,” followed by a 4.0 for CBS for “Criminal Minds.” NBC and ABC tied for third that hour at 2.2, NBC for “Deal or No Deal” and ABC for a repeat of “Lost,” with Univision fifth with a 1.6 for “Mundo de Fieras” and CW sixth with a 1.5 for “One Tree Hill.”
 
ABC took the lead at 10 p.m. with a 5.7 for “Lost,” up slightly from last week’s season-low 5.6. CBS was second with a 4.1 for “CSI: NY,” NBC third with a 2.5 for “Medium” and Univision fourth with a 1.2 for “Don Francisco Presenta.”
 
Among households, Fox finished first for the night with a 17.3 average rating and a 26 share. CBS was second at 8.2/13, NBC third at 4.8/8, ABC fourth at 4.8/7, Univision fifth at 2.1/3 and CW sixth at 1.9/3.