Coconino National Forest officials elevated the fire risk in the Sedona area to very high.
The critical designation comes after fire risks were only recently elevated and the National Weather Service forecasted a hot dry monsoon in northern Arizona.
It means officials expect even small fires to spread quickly and burn more intensely.
On Thursday, the entire national forest and the city of Flagstaff will enter Stage 1 restrictions, limiting wood fires to developed camp sites and barring smoking.