On Monday morning, Mineral County residents awoke to smoke so thick it was difficult to see from one end of E Street in Hawthorne to the other. The cause of the smoke?

The Aspin Fire in California.

The fire, which has consumed more than 11,000 acres, was started by a lightning strike and discovered on July 22.

The fire is 20 percent contained, and crews expect it to be fully contained by Aug. 10. Almost 1,500 firefighters and support staff are working to get the blaze under control.

Lyn Sieliet, a spokeswoman for the US Forest Service, said the Aspin Fire was one of about 19 fires that started when a lightning storm moved through the Mammoth Lakes area.

Sieliet said the fire is burning in a difficult area, and crews are using indirect methods to fight the fire. Indirect methods of firefighting involve digging trenches and clearing trees and brush to starve the fire of its fuel.

“They’re trying to get a line or a buffer zone all the way around the fire, so at this point they have 20 percent of that line construction,” Sieliet said on Monday.

Smokey conditions are expected to let up on Wednesday and Thursday, but after that, it’s anyone’s guess what the wind will do, said Marvin Boyd, a meteorologist with the National Weather Service.

Boyd said weather models show winds picking up in the Hawthorne area on Wednesday and Thursday, which should clear the smoke out. However, by Friday, he expects conditions to return to normal, and the smoke to settle in again.

But, Boyd said, weather prediction models are only accurate for four days. He said people should expect the smoke to be worse in the mornings and at night.

“It’s probably going to get a little worse before it gets better,” he said. “They’re planning to do some burn operations at the fire site. They’re trying to turn the fire in on itself.”

While the smoke is heavy, sensitive people should stay inside as much as they can.

Wanda Nixon, Community Health Nurse and Mineral County Health Officer, said it’s important to avoid heavy exercise when the smoke is heavy.

“Running, playing basketball, or soccer, or something like that would not be advised,” she said.

People who are outside and experience coughing; a sore throat; eye irritation; or a runny nose should see a doctor, Nixon said.

Nixon said the people most at risk of having difficulty are those with chronic respiratory problems, like Chronic Obstructive Pulmonary Disease or asthma; the elderly and the young.

“It affects young ones more because they have immature respiratory systems,” Nixon said. “They’re prone to asthma and allergy.”

Nixon said when the smoke is no longer visible and the odor has left the air, it’s usually safe to start going outside again. But, she cautioned, the main worry when it is smokey outside is the fine particles that accompany the smoke, which can sometimes be neither seen nor smelled.

They can also get into people’s homes, Nixon said. When it’s smokey, people should avoid “stirring things up” by doing things like vacuuming, she said.

The smoke is at its worse in the mornings and at night because of the inversion barrier, Boyd said.

In the warmth of the day the sun bakes the ground and the air alike, and both are hot, Boyd said.

At night, especially during the summer, the temperature of the ground is lower than the temperature of the air, because the ground releases its heat faster than the air.

The rising heat creates a barrier through which the faster moving winds higher in the atmosphere cannot pass. This barrier, which Boyd called an induction barrier, keeps the smoke in lower lying areas, like the valleys and basins of Mineral County.

As the day goes on and the heat from the sun warms up the ground, the temperatures in the air and ground come closer together, and the induction barrier is breached, allowing the faster winds to carry the smoke away, Boyd said.