Caldor Fire near Tahoe is 98% contained, but it’s getting smokier


If you’re headed toward South Lake Tahoe this week, you shouldn’t be too worried if a smoky haze settles in as you drive inland — despite the recent wildfire that ravaged the Sierra Nevada slopes along the way, U.S. Forest Service officials say.

Although the Caldor Fire, which burned more than 220,000 acres to the southwest of Lake Tahoe over two months, is now 98% contained, some of the areas it charred are still producing smoke and ash. It’s particularly visible when heading along Highway 50 toward and through the Sierra.

There are three reasons for the smoky air, fire officials explained:

The weather

While Truckee and the Tahoe region received a dusting of snow over the weekend, it wasn’t near enough to smother California’s lengthy fire season. The Caldor Fire burn scar received rain and snow for only about six hours — and it’s usually how long the precipitation falls, rather than how much, that determines whether it helps firefighters.

Gusty winds are also blowing pine needles into the burn area, occasionally igniting but rarely creating a big fire. The National Weather Service issued a red flag warning for the first half of the week — meaning increased fire risk due to bone-dry conditions and high wind speeds.

The smoke won’t be particularly bad in the Bay Area, said Gerry Diaz, a weather service meteorologist.

Smoke won’t be swept into the area because the winds are coming down from the Pacific Northwest.

“Usually, we have a northeasterly flow and higher chances of smoke making it out here, but this system is at an angle, a more northerly direction,” Diaz said.

Burned tree “cigars”

Driving up Highway 50, you’ll see scorched tree trunks. Those charred logs may still have embers smoldering inside and occasionally fall, weakened by fire damage.

When that happens, expect to see increased smoke and perhaps some flames as the fire consumes the rest of the wood. “It can definitely be surprising and even a bit
unsettling to see the increased smoke so long after the initial fire burned through the area,” Caldor Fire officials said in a recent update.

But there are few other fuels on the ground at this point in the year, according to the U.S. Forest Service, so don’t expect those small fires to turn into bigger conflagrations.

Contained vs. controlled vs. extinguished

Although the Caldor Fire is 98% contained, that doesn’t mean it’s extinguished.

Containment means that the fire is no longer progressing forward and burning new land. Firefighters create a control line and the blaze is burning within those lines, and any spot fires that pop up are quickly put out, according to the National Wildfire Coordinating Group.

If a fire is controlled, the conflagration is unlikely to jump the bounds of the control line and firefighters have removed any fuel close to the line.

When a blaze is extinguished, it means no new hot spots have appeared in the past 48 hours.

But because flames from the Caldor Fire are still burning, you’ll likely see some smoke in the air, officials say.

They offered further reassurance: More than 1,000 personnel are still working on the fire, and are reporting success daily in suppression, repair and rehabilitation efforts.

However, because conditions remain extremely dry throughout the fire footprint, “it will be quite a while before the large number of interior hot spots are eliminated,” the update said.

Gwendolyn Wu is a San Francisco Chronicle staff writer. Email: