British-Australian swimmer Penny Palfrey is to launch a historic attempt to swim across the shark-infested waters from Cuba to the United States, but bad weather could affect her plans. Palfrey, a 49-year-old mother of three and grandmother of two, is vying to become the first person to make the 103-mile (165-kilometer) swim across the Florida Straits without a shark cage. She is scheduled to set off after dawn Friday from the Hemingway International Yacht Club in western Havana, headed for Florida\'s Key West. The journey is expected to take three days. In September 2011, veteran US endurance swimmer Diana Nyad, 62, quit her swim two-thirds of the way across the strait from Havana, after suffering dangerous jellyfish stings. It was her third failed attempt to complete the trek, which she first attempted at age 28. Like Nyad, Palfrey will swim without a shark cage. The dual British-Australian national admitted at a press conference on Thursday that she faced multiple obstacles but hoped her experience would help carry her through the swim. Inclement weather however could alter her plans. Torrential rains and lightning, which started in Havana on Thursday, are in the forecast until Monday, according to Cuban meteorologists, although weather conditions can change quickly in the region. Palfrey, who was born in Britain and moved to Australia at age 19, is among the most accomplished open-water swimmers in the world and has successfully completed swims in the Caribbean and Pacific without a shark cage. Two years ago, she crossed the Strait of Gibraltar between Spain and Morocco in three hours and three minutes, setting a new record for women. Last year, Palfrey -- who began swimming at age nine -- swam from Little Cayman to Grand Cayman Island without a shark cage.