A Red Flag Warning means high temperatures, very low humidity and stronger winds are expected to combine making an increased risk of fire danger.
Red Flag Status for Grass Valley & Nevada City, CA
Another weather pattern that would spawn a Red Flag Warning is dry lightning. This is where lightning strikes are expected with little to no rainfall. This is most common in California and the Western States during the summer months.
It doesn’t take much wind to start a fire during dry conditions. Anything over 15 mph is adequate when the relative humidity is very low.
The following is a list of things you should avoid when a Red Flag Warning has been issued: