“So You Think You Can Dance” may just be this summer’s “Dancing With the Stars,” that is, the summer’s biggest hit. The second-year Fox reality show continued to grow last night in its second Wednesday outing.

“Dance” averaged a 4.2 overnight rating last night among adults 18-49, up 17 percent over last week’s 3.6 rating. It easily won its 9 p.m. timeslot over NBC’s original “Dateline,” which averaged a 3.3.

“Dance,” which placed its Wednesday and Thursday shows in last week’s top five among 18-49s, has been performing very well after a decent first run last summer.

Last night’s 4.2 was a full point better than the 3.2 the show averaged last year. It also bettered Fox’s summer 2005 average in the Wednesday 9 p.m. slot, a 2.6, by 62 percent.

“Dance” led Fox to an easy win on an otherwise slow night, averaging a 3.3 rating and 10 share. It was followed by NBC at 2.8/8, CBS at 2.2/7, Univision at 1.6/4, ABC at 1.5/4, UPN at 0.8/2 and the WB at 0.7/2.

At 8 p.m., Fox’s repeat of last week’s “Dance” episode finished No. 1 with a 2.5 rating. The first hour of NBC’s “Dateline” was second at 2.4, followed by a 1.9 for CBS’s “Gameshow Marathon,” which fell 17 percent from last week. ABC’s “George Lopez” and “Freddie” reruns combined for a 1.8, tying with Univision’s “La Fea Mas Bella,” while the WB posted a 0.9 for “Blue Collar TV” and UPN averaged a 0.8 for “Gang of Roses.”

At 9 p.m., Fox’s 4.2 for “Dance” led, followed by the 3.3 for “Dateline.” CBS was third at 2.2 for a “Criminal Minds” repeat, followed by Univision’s 1.7 for “Barrera de Amor,” ABC with a 1.3 for a “Lost” repeat, UPN with a 0.8 for “Roses” and the WB with a 0.4 for a “One Tree Hill” rerun.

At 10 p.m., CBS led with a 2.7 for a “CSI: NY” repeat, followed by NBC at 2.5 for a “Law & Order” rerun. An original “Commander in Chief” on ABC mustered just a 1.4, 0.2 ahead of Univision’s “Don Francisco Presenta.”

NBC finished first with a 5.6/10 in households, followed by CBS at 5.4/9, Fox at 5.3/9, ABC at 3.1/5, Univision at 1.9/3, UPN at 1.4/2 and the WB at 1.1/2.