SPOKANE, Wash. -

Thunderstorms are expected to drop up to half an inch of rain Wednesday on the largest wildfire in the state's history. But that won't be enough to extinguish the flames.

Andrew Sandri, spokesman for the Carlton Complex of fires, says it would take a lot more water than that to put out the flames.

The wildfire stands at more than 250,000 acres, nearly 400 square miles, and is being fought by about 2,500 personnel.

Sandri says the rain will certainly help firefighters make progress. But lightning could also spark new fires in the parched region. And all the moisture could lead to flash floods because so much ground vegetation has been lost.

Sandri says the fire remains at 16 percent contained, as crews concentrate on strengthening existing fire lines.