As bad as last year's record-shattering fire season was, the western U.S. starts this year's in even worse shape.

The soil in the West is record dry for this time of year. In much of the region, plants that fuel fires are also the driest scientists have seen. The vegetation is primed to ignite, especially in the Southwest where dead juniper trees are full of flammable needles.

"It's like having gasoline out there," said Brian Steinhardt, forest fire zone manager for Prescott and Coconino national forests in Arizona.

A climate change-fueled megadrought of more than 20 years is making conditions...