Why one statewide "fire season" is a simplification
CAL FIRE and local agencies increasingly describe California as having a year-round fire risk rather than a single season, but the practical calendar for any given property still depends heavily on its microclimate. Coastal Southern California, with its Santa Ana wind exposure, can see critical fire weather into December; the interior Central Valley and foothills typically peak earlier, as grasses cure by early summer; and higher-elevation and northern forests often peak latest, after summer heat has dried heavier fuels.
That matters for scheduling fuel-reduction work, because "get it done before fire season" is really several different deadlines depending on where the property sits — and vegetation itself grows and cures on different timelines across those same zones.
A rough regional guide
Coastal and Southern California chaparral typically cures by late spring and stays flammable through fall Santa Ana events, so late-spring and summer clearing timed ahead of red-flag season is standard. Central Valley and foothill grasslands cure earlier — often by May or June — making late-spring grazing the priority window before that fuel is fully dry. Northern California's mixed conifer and brush country generally peaks later in the summer as heavier fuels dry out, and the Sierra foothills carry real risk into fall.
None of this replaces a site-specific defensible-space plan — CAL FIRE's own guidance and a local fire authority's inspection are the actual authority for any given property — but it explains why the "book early" advice repeated across fire-safety guides isn't generic caution: the window really is different depending on where the fuel is and how fast it cures.