Burton recorded a 3-under 69 during the second round to move to 8-under for the tournament. She now holds a one-shot advantage over Sorenstam, who struggled to an even-par 72. Laura Diaz (68) and Danielle Ammaccapane (69) are tied for third at 6-under.
Damp weather plagued players for a second day and higher scores were reflective of the conditions.
Rain delayed the second round for nearly two hours Friday and darkness finally suspended play with 24 players left on the course. The action will resume Saturday at 8 a.m. EDT with round three scheduled to begin at 10 a.m.
Sorenstam had a tough day. After opening in 65, the Swede teed off the backside, making five consecutive pars. She fell into trouble on the par-4 15th, making back-to-back bogeys through 16, but in typical Annika-style she recovered with par on the 17th and made the turn after recording birdie on the 18th.
Despite another dropped shot at the par-4 first, she eagled the par-5 seventh by sticking a 4-wood to five feet to move within one of the 36-hole lead.
Burton recorded five birdies to overcome a pair of bogeys Friday.
'I guess you can say I'm kind of a mudder,' said Burton. 'A couple of my wins have been in pouring down rain. You just have to concentrate. We've had to learn to deal with tough conditions. You're not always going to have perfect weather out here.'
Full-field scores from the Aerus Electrolux Championship