Eight players failed to break 80 in Saturday's taxing conditions, while 11 players broke 70, most of them in the morning before the wind began to strengthen.
The 22-year-old Joo shot a three-under 68 second round to get to eight under 134 in the ShopRite LPGA, one of two LPGA tournaments played over 54 holes.
Joo needed only 25 putts and dropped only one shot, on the opening hole.
"I almost shank my 3-wood on the first tee. I mean, it looked way bad because of the wind," she said.
"I knew that it was going to play as a different golf course, like a totally different golf course comparing to yesterday, so I was trying to stay mentally calm and also physically calm, too.
"I started playing golf because I want to win a tournament on LPGA, so it will be super fun, very exciting. But right now I just want to get a hot shower. So cold, yeah. Freezing."
Japanese twins Chizzy and Aki Iwai each scratched out a 68 and were in the group of players four shots behind that included Celine Boutier of France (72), Somi Lee of South Korea (69) and Israeli player Laetitia Beck, who started with a one-shot lead and tumbled to a 75.
"Today was extremely windy, so definitely was much harder to judge club selections, and putts were also much harder," Beck said. "That's where I pretty much struggled today. I didn't make putts."
Cassie Porter shot a 70 to be the leading Australian, tied for 17th, sevens shots behind Joo, while Robyn Choi had a 71 and was a shot further back, Gabriela Ruffels (73) was at two over and Steph Kyriacou (74) was three over.
Charley Hull, at No. 7 the only player from the top 10 in the world, followed a 74 with a 75 and missed the cut.
This field is on the weaker side mainly because of scheduling. The New Jersey tournament is a week before the U.S. Women's Open across the country at Riviera in Los Angeles.
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