The massive Dixie and Caldor fires burning in the Sierra are now about 65% contained, but crews says the threat of spread is increasing as the moisture from recent rainfall dries up, making forest fuels more flammable, and high winds are forecast for the coming days.

Firefighters continued to make progress on the Caldor Fire, reaching 65% containment as of this morning, and holding the lines south of the Tahoe Basin and east of the Kirkwood Mountain Resort.

Cal Fire officials said the fire remained active overnight as downed timber and dried-up vegetation continued to smolder and burn. Firefighters mopped up hot spots near fire control lines, but southwest winds expected today through next week are making it challenging to keep to the existing control lines, they said. Acting as bellows, the high winds expected this week could worsen fire activity for emergency crews.

On the fire’s eastern edge, conditions overnight were mild, with southwest winds shifting south during the night. The fire mostly smoldered and creeped slow on the surface, and crews continued to patrol and improve fire lines from Trimmer Peak down to Highway 89. Crews were also patrolling Christmas Valley, while others were assigned to patrol the area around Caples Creek in an effort to protect Kirkwood.

Near Lake Almanor, the Dixie Fire — by far the largest this fire season, and the second-most destructive in California history — is also 65% contained with favorable weather conditions aiding firefighters, who are looking to keep the fire’s edge from structures in the Grizzly Peak area.

On Saturday, officials said firefighters surveyed and reinforced containment lines and prepared for an expected increase in fire activity as the weather warms and dries. East of Milford, fire crews were attempting to prevent flames from again affecting that community and Highway 395.

Firefighters are set to work today to improve some mountain roads as secondary control lines, as well as strengthen their work on a direct attack in the rugged Devil’s Punchbowl.

On the fire’s western edge, the overnight weather and humidity helped moderate the fire. Winds were calm with clear skies, and temperatures dropped into the 30s, with humidity rising to about 70%.

Although battling in steep and rugged terrain in some parts of the fire, there were no reports of spot fires over the containment lines overnight. On Sunday, firefighters will concentrate on building containment lines on the northern part of the fire as well as reinforce containment lines throughout the rest of the fire.

This is a developing story. Check back for updates.