Fire blankets US tourist spot in smoke

Ash has rained down on Lake Tahoe and thick, yellow smoke has blotted out views of the mountains rimming its pristine blue waters as a massive wildfire threatens the holiday spot on the California-Nevada state line.

Tourists ducked into cafes, shops and casinos for a respite from hazardous air coming from the erratic blaze about 30 kilometres away.

The Caldor Fire erupted over the course of a week into the nation’s No.1 firefighting priority and was “knocking on the door” of Tahoe, said Thom Porter, California’s state fire chief.

A major wildfire has not penetrated the Lake Tahoe Basin since 2007.

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No evacuations have been ordered and Porter said he did not think the fire would reach the lake.

However, it was impossible to ignore the blanket of haze so severe that it closed schools for a second day in Reno, Nevada, which is about 100km from the fire.

An army of firefighters worked to contain the blaze, which has spread explosively in a manner witnessed in the past two years during extreme drought.

Northern California has seen a series of disastrous blazes that have burned hundreds of homes and many remain uncontained.

On Tuesday, President Joe Biden declared that a major disaster exists in California and ordered federal aid be made available.

The Caldor Fire had scorched more than 490 square kilometres and destroyed at least 455 homes since August 14 in the Sierra Nevada southwest of Lake Tahoe.

It was 11 per cent contained on Tuesday and threatened more than 17,000 structures.

Nationally, 92 large fires were burning in a dozen states, according to the National Interagency Fire Center.

Although many fires are larger, the Caldor Fire has become the top priority to keep it from sweeping into the Tahoe.