Four consecutive years of drought, millions of dead trees and dry vegetation means the threat of wildfires will remain high in Central and Southern California and the Southwest in July and August.
The National Interagency Fire Center and National Predictive Services unit released its National Significant Wildland Fire Potential Outlook report Friday.
The report looks at fire risk from July through October.
It says parts of the intermountain West also face "Above Normal" chances of significant fires in July because grasses and small trees are dry. The area includes northern California and parts of Idaho, Montana, Nevada and Wyoming.
"Robust fine fuel crops will continue to drive the significant fire potential across the Southwest, the Great Basin, the northern Plains and California," forecasters say. "These fine fuel crops will lead to periods of increased fire activity, larger fires and more rapid rates of spread throughout fire season especially when associated with dry and windy periods."
Fire potential is also increased for mountain areas of California and offshore winds in the fall months are a concern.
"In September and October, long term drought is expected to remain in place and fall conditions typically bring an increase in offshore wind events that often drive fire activity for the state."
Southern and central California also will continue to have "Elevated" or "Above Normal" fire potential through October due to long-term drought, severe tree mortality, and vegetation mortality.
"Current conditions [southern and central California] in the field with both live and dead fuels are more in line with readings seen in August or early September," the report notes.
"Fuel conditions are expected to continue to support large fires as all fuel types will readily accept flame. There is also a growing dead fuel component across a wide swath of the region. There is a mass die-off of vegetation, especially in the Sierra, where an estimated 66 million trees are dead or are dying due to the drought and an outbreak of the bark beetle."
The report says "remaining live vegetation is severely stressed and ongoing precipitation deficits have limited live fuel moisture."
"This condition will lead to continuous elevated potential for significant fires throughout the outlook period. Fine fuels in these ecosystems benefited from well-timed spring precipitation to establish a more continuous fuel bed than in previous summers. This will increase the chances of more rapid rates of spread and larger fires, especially when associated with favorable topography or during dry and windy periods."
Forecasters say the risk level will likely return to normal in most areas in September, but they say California could remain at risk into the autumn because of four consecutive years of drought.
"Little to no rainfall is expected from July through September in Northern California," the report says. "October is expected to be drier-than-normal. Temperatures will generally be above normal during this time. Lightning amounts are expected to be near or possibly below normal this fire season."
The National Interagency Fire Center reported that crews were battling 20 large, active wildfires in 12 states covering more than 138,000 acres. NIFC reports more than 2.1 million acres have burned year-to-date.
"Areas west of the Cascade-Sierra crest and below 3000 feet from Mendocino and Shasta Counties southward will see significant fire potential increase to Above Normal in July, and remain Above Normal in the August-October timeframe," according to the forecast. "Valleys and foothills east of the crest will also increase to Above Normal in July and remain that way through October. The remainder of the region is expected to see normal significant fire potential."