SCOTTS VALLEY (CBS SF) — Firefighters battling the CZU Lightning Complex fire in the timber-rich Santa Cruz Mountains increased containment to 76 percent overnight, but soaring temperatures, bone-dry humidity levels and a Red Flag Fire Warning Monday raised new concerns along the fire lines.

Cal Fire CZU Operations Chief Jeremy Pierce said the fire challenged the containment lines on Sunday, especially around 1 p.m. when temperatures soared further drying out the material matting the forest floor.

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“For everyone out there yesterday, you are aware that there was quite a lot of work for everybody,” Pierce said at the command post Monday morning briefing. “Crews worked very hard yesterday, picking up all the smokes (smoldering materials on forest floor), all the hot spots.” In the Loma Mar area, there was a lot of mop-up in that area and it did hold.”

“With the increase in the heat, decrease in humidity and the ignition points rising, we did have quite a bit of smokes that popped up in the afternoon. We had one slop over (flames jump over a fire line) of about 1/2 acre…which was picked and taken care of. Additionally, there is some significant potential for some of those islands (of fire) to get going and get a little more established and get up in the canopy for a re-burn.”

The fire had burned 86,509 acres by Monday morning. Damage inspection crews had completed their assessments in the fire area by Sunday with the final total of homes destroyed at 925 — most of those in Santa Cruz County. In all, 1,589 structures had been destroyed and one person — an elderly resident of the Last Chance area near Davenport — had died.

While thousands of residents have been allowed to return to their homes, there still remained some evacuation zones in both San Mateo and Santa Cruz counties.

Click For Updated Evacuation Zones and Other CZU Complex Information

Meanwhile, containment grew on the region’s two largest fires — the LNU Lightning Complex in Wine Country and the SCU Lightning Complex still burning mostly in Santa Clara County.

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SCU Lightning Complex Fire

Containment of the SCU Complex fire — the second largest wildfire outbreak in state history — grew to 93 percent overnight with full containment now projected for Sept. 12th. It has burned 396,624 acres, destroyed 136 structures and left five people injured — three firefighters and two civilians.

The soaring temperatures were also challenging efforts to surround the fire zone.

“Hot dry conditions allowed for increased smoldering of hot material in the interior portions of the complex,” Cal Fire officials said in a Monday release. “Temperatures across the complex ranged between 110 and 103 with humidity in the low teens and single digits.”

As the containment of the blaze has grown, fire crews from around the state and the country have been allowed to return home. On Monday, there were 819 firefighters manning the lines including a contingent from the California National Guard.

LNU Lightning Complex

By Monday morning, the LNU Lightning Complex fire had grown to 375,209 acres — the third largest in state history — and was 91 percent contained. It has been the deadliest of the fires, claiming five lives — three in Napa County and two in Solano County.

The complex has destroyed 1,491 structures including 309 homes in Solano County, 305 in Napa and 159 in Sonoma County.

There were still 1,563 firefighters including National Guard troops manning the fire lines.

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“All evacuations within the complex have been lifted,” Cal Fire officials said in a Monday morning news release. “The fire continues to have limited growth on both the Walbridge Fire and Hennessey Fire. Crews will continue to work to reinforce containment lines and fire suppression repair teams remain active throughout the area.”