Professor Sally Thompson was asked, "So are wet winters worse for fires? Or are dry winters worse?"
The answer to both questions, is yes.
“Regardless of winter precipitation, wildland fuels inevitably are desiccated and ready to burn by late summer and fall,” Thompson says. “The risk is better calculated from a daily rather than an annual perspective—what the humidity is, and what the winds are doing on a particular day."
Thompson adds that fire risk is increasing in California for two reasons: climate change and the increased growth of “interface” in wildland areas.
Climate change clearly is leading to drier, warmer conditions over the long term, translating to longer fire seasons.
And the expansion of residential and commercial developments into wildland areas means that fires that would’ve done nothing more than burn brush and grass 10 or 20 years ago now pose significant risk to human lives and valuable homes.
See "Are Wet Winters or Drought Worse for California Fires?" (California, Cal Alumni Assoc. magazine, 11.20.17)