The huge wildfire burning around Yosemite National Park, known as the Rim Fire, has now consumed nearly 225 square miles (362 square kilometres). It is estimated to be just 7 percent contained.
Hundreds of firefighters were deployed Sunday to protect Tuolumne City and other communities in the path of the Rim Fire.
The fire continues burning in the remote wilderness area of Yosemite, but park spokesman Tom Medena said it's edging closer to the Hetch Hetchy Reservoir, the source of San Francisco's famously pure drinking water.
Despite ash falling like snowflakes on the reservoir and a thick haze of smoke limiting visibility to 100 feet (30 metres), the quality of the water piped to the city 150 miles (241 kilometres) away is still good, say officials with the San Francisco Public Utilities Commission.