Several daily buses run from Vientiane to Luang Prabang, taking 11–13 hours. The road from Huay Xai to Luang Prabang is poorly maintained, remote, unlit, unmarked and dangerous for the unfamiliar, particularly in the wet season. Buses regularly travel the route in 14–16 hours. If coming from Vietnam, sleeper buses can be caught from Hanoi to either Luang Prabang or Vang Vieng. The Mekong River itself is also an important transportation link. At Chiang Khong it is possible to hire a barge to cross the river. A trip from Huay Xai, across from Thailand, downstream to Luang Prabang takes two days by slow boat, typically with a stop at Pakbeng. Luang Prabang will be served by the Vientiane–Boten railway from the end of 2021. The railway parallels Route 13, and will serve as Laos' first major north-south railway line, from Boten at the Chinese border in the north to Vientiane in the south. The complete journey is expected to be less than three hours by train instead of three days by road. Luang Prabang features a tropical wet and dry climate ("Aw") under the Köppen climate classification. While the city is generally very warm throughout the year, it is noticeably cooler during December and January. Luang Prabang also experiences wet and dry seasons, with the wet season from April until October, and the dry season during the remaining five months. The city receives approximately of precipitation annually.