When the air is warm and dry, transpiration and evaporation also suck water out of the plants and soil. That leaves dry vegetation that can provide fuel for flying embers to spread wildfires, as the Los Angeles area saw in early January.

The state is seeing a sharp water divide this year, with lots of rain in the north while the south has stayed dry. A hydrologist explains what’s happening.

Parts of Santa Monica were ordered to be evacuated as fast-moving flames destroyed homes along the coast in Los Angeles. Winds were picking up overnight, potentially fueling the fires.