Above: map showing minimum relative humidity levels predicted for Saturday in the Western United States. Red Flag Warning areas are in Utah and Northern California. NWS.
The official Red Flag Warnings for Saturday only include portions of Utah and Northern California, but low humidities will be prevalent across most of the southwest one-quarter of the country. Generally, the winds will not be especially strong, which is probably what kept the Red Flag Warning areas from being larger than they are.
Very high to extreme fire danger levels are predicted for large portions of Utah, Colorado, Arizona, and New Mexico, as well as the lower elevations in Northern California.