The US National Weather Service has issued a “red flag warning” for areas of the West Coast, as high winds threaten to spread devastating wildfires still further.

Gusts of up to 40 mph (64 km/h) are expected in parts of southern Oregon, with no rain.

Fires have been raging for three weeks in Oregon, California and Washington, burning land and destroying homes.

Tens of thousands of people have had to flee and at least 33 have died.

Dozens of people are missing in Oregon alone, with one emergency official saying the state should be preparing for a “mass fatality incident”.

Cooler, moister conditions on Saturday allowed firefighters to make some progress with the fires.

However, the forecast for Sunday prompted a warning of winds of 15-25 mph and gusts of 30-40 mph in the Shasta Valley and east of the Southern Oregon cascades.

A red flag warning is the highest alert for events which could result in major fires, and which demands extreme caution by residents.

This area includes Jackson County, Oregon, where the Almeda fire has destroyed hundreds of homes and remains only 50% contained.

The fires have so far scorched an area of land the size of New Jersey, officials say.

The smoke pollution from the wildfires has left Oregon’s largest city, Portland, with the worst air quality in the world, followed by San Francisco and Seattle, according to recent findings from IQAir.