South Lake Tahoe saw Thousands of people rushing to flee as the entire resort city came under evacuation orders after wildfire raced toward Lake Tahoe, a large freshwater lake straddling California and Nevada.

The authorities had issued evacuation warnings for the city of 22,000 on Sunday but they were turned into orders on Monday. Vehicles loaded with bikes and camping gear and hauling boats were stuck in traffic, stalled in hazy, brown air that smelled of campfire. Police and other emergency vehicles whizzed by, Associated Press reported.

"This is a systematic evacuation, one neighborhood at a time. I am asking you as our community to please remain calm," South Lake Tahoe police Lt. Travis Cabral said.

The new orders were issued just a day after communities living several miles south of the lake were ordered evacuated as the Caldor Fire raged nearby.

South Lake Tahoe's main medical facility, Barton Memorial Hospital, proactively evacuated 36 patients needing skilled nursing and 16 in acute care beds Sunday, sending them to regional facilities far from the fire, public information officer Mindi Befu said. The rest of the hospital was evacuating following Monday's expanded orders.

The Lake Tahoe area in the Sierra Nevada mountains is a recreational paradise for San Francisco Bay Area locals looking for a weekend getaway, as well as a national destination. The area offers beaches, water sports, hiking, ski resorts and golfing.

South Lake Tahoe, at the lake's southern end, bustles with outdoor activities, with casinos available in bordering Stateline, Nevada.

The region faces a warning from the National Weather Service about critical fire weather Monday and Tuesday.

The last major blaze in the area took South Lake Tahoe by surprise after blowing up from an illegal campfire in the summer of 2007. The Angora Fire burned less than 5 square miles (13 square kilometers) but destroyed 254 homes, injured three people, and forced 2,000 people to flee.

The Caldor Fire has scorched 277 square miles (717 square kilometers) since breaking out on August 14. After the weekend's fierce burning, containment dropped from 19% to 14%. More than 600 structures have been destroyed, and at least 20,000 more were threatened.

It's among nearly 90 large blazes in the US. Many are in the West, burning trees and brush sucked dry by drought. Climate change has made the region warmer and drier in the past 30 years and will continue to make the weather more extreme and wildfires more destructive, according to scientists.