STATE COLLEGE, Pa. (AP) -- Whether in cold, blustery Iowa City, or soggy Happy Valley, Iowa has Penn State figured out.
The Hawkeyes upset the fifth-ranked Nittany Lions for a second straight year, with Adrian Clayborn returning a blocked punt for a touchdown in a 21-10 victory on Saturday night.
A season after a stunning 24-23 win at chilly Iowa knocked then-unbeaten Penn State out of the national title race, the Hawkeyes (4-0, 1-0 Big Ten) handed Penn State (3-1, 0-1) its first loss of the season again. This time, they beat them in a defensive slugfest played in a drenching rainstorm, capped by a 16-point fourth-quarter flourish.
''The team really proved to be a resilient bunch tonight because there was nothing easy about anything that happened out there,'' Iowa coach Kirk Ferentz said.
The Hawkeyes have won seven of their last eight against Penn State.
After falling behind 10-0 in the first quarter, Iowa's defense clamped down on quarterback Daryll Clark and the Penn State spread HD offense with withering pressure. Broderick Binns ' sack led to a safety in the second quarter.
A 6-foot-3, 282-pound defensive end, Clayborn rumbled 53 yards after blocking the punt to give Iowa an 11-10 lead with 12:21 left.
The big guy was huffing and puffing as teammates surrounded him in the end zone.
''I was too tired to celebrate,'' the junior said. ''I was just trying to get to the sideline so I could sit down.''
Clark was intercepted on the next drive to set up Adam Robinson 's 13-yard touchdown run to put the Hawkeyes up 18-10 with 8:32 left.
It only got worse down the stretch for Penn State.
A 36-yard punt return by Chaz Powell , plus a 15-yard personal foul penalty gave the Nittany Lions the ball at the Iowa 36 after Robinson's touchdown.
But tailback Evan Royster fumbled the ball away on the next play.
''I thought the kids hung in there, tried to come back, and they kept making mistakes,'' Penn State coach Joe Paterno said.
Clark was intercepted again with four-plus minutes left.
It was a disappointing end to a strong start for Clark, who connected with Powell for a 79-yard touchdown pass on Penn State's first offensive play of the game.
Later in the first, Penn State opened up the offense by running Clark on keepers and methodically marching down the field on a 20-play, 10-plus minute drive that ended with Collin Wagner 's 27 yard-field goal for a 10-0 lead with 52 seconds in the first quarter.
After hitting his first five passes, Clark finished 12 of 32 for 198 yards with one TD and three interceptions. The senior had vowed earlier in the week to atone for his poor performance last year at Iowa, in which he was 9 of 23 passing for 86 yards and one interception.
Paterno said blame shouldn't be assigned just to his quarterback.
''It was a team loss. No one person, or one play lost it,'' Paterno said. ''We got licked.''
Ricky Stanzi finished 11 of 26 for 135 yards and two interceptions for Iowa, and Robinson had 88 yards on 19 carries.
After opening the season with victories over three weak nonconference opponents, the Nittany Lions ' offense failed its toughest test yet in the Big Ten opener.
On defense, Penn State star linebacker Sean Lee (left knee) didn't play, but the team got a boost from the return of fellow standout Navorro Bowman from a right groin injury. They held an opponent without a touchdown in the first half for the fourth straight game.
Bowman and fellow linebacker Josh Hull combined for 26 tackles, including five for losses.
Iowa did manage 163 rushing yards on the Nittany Lions ' D, yet the Hawkeyes couldn't convert into scores until late.
Their defense was just as stout, and Iowa's special teams outplayed Penn State.
In the second quarter alone, the Hawkeyes outgained Penn State 124 to minus-6.
After a nice start, Penn State had three straight three-and-outs in the second, including Binns' sack of Clark in the end zone that led to the safety.
Pat Angerer led the active Iowa defense with 14 tackles, one forced fumble and the 38-yard interception return that set up Robinson's TD.
''I got scared a little running around trying to find a place to go,'' Angerer said. ''We were out there flying around, trying to do our job.''
The Hawkeyes ruined Penn State's ''Whitehouse,'' in which the school asked its fans to wear white team gear. Over 109,000 people packed Beaver Stadium.
In the end, it was the loud Iowa fans in bright yellow clothing that stood out in sad Happy Valley.