The cables to the summit of Half Dome in Yosemite National Park will be reset Friday — a full week ahead of schedule.

That will provide a one-week window to reserve climbing permits for those who missed out on advance sales for the regular climbing season. The sale for these permits, to ascend Half Dome between May 16 and May 22, starts at 10 a.m. Wednesday at www.recreation.gov (recommended) or call (877) 444-6777 (not recommended), first-come, first-served.

Climbing permits are required to ascend the cables at Half Dome, help ease congestion, and are non-refundable and non-transferable so no one can game the system.

Permits for the regular season were available through a lottery during the month of March. Approximately 50 permits per day will be available on a daily basis.

For more information regarding the lottery and the Half Dome cables, go to www.nps.gov/yose/ planyourvisit/halfdome.htm.

The trail to Half Dome from Yosemite Valley is a strenuous hike that is a 17-mile round trip with an elevation gain of 4,800 feet. The trail is routed passes Vernal Fall, Nevada Fall, Liberty Dome and Little Yosemite before reaching the cables on Half Dome’s steep granite shoulder. Metal cables and wooden planks are placed along the steep shoulder of the dome to assist hikers to the summit.

“Visitors are advised to take appropriate precautions when planning a hike of this length and difficulty, and to be prepared for changing weather and trail conditions,” said Kari Cobb at park headquarters. “Thunder and lightning are common occurrences in the High Sierra during the summer and fall seasons. Hikers should not attempt to summit Half Dome when rain or thunderstorms are forecasted and are advised to use extreme caution when the rocks are wet.”

Tom Stienstra is The San Francisco Chronicle’s outdoors writer. E-mail: tstienstra@sfchronicle.com. Twitter: @StienstraTom

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