Motorists stop to observe the Walbridge fire, part of the larger LNU Lightning Complex fire, from a vineyard in Healdsburg, California, on Aug. 20, 2020. A series of massive fires in northern and central California forced evacuations as flames quickly spread, darkening the skies and polluting the air.
Credit: © Josh Edelson, AFP/Getty Images

Wildfires have ravaged the U.S. state of California, killing at least 5 people and forcing thousands to evacuate (leave) their homes. Fueled by a heat wave and sparked by lightning strikes, the wildfires have set the state ablaze and covered the air in thick smoke.

Wildfire is the uncontrolled burning of large areas of vegetation. Wildfires may be ignited by human activities or by natural causes. Such natural causes include lightning, volcanic activity, or even intense sunlight. Wildfires occur on every continent except Antarctica. They are most common in the temperate forests and grasslands midway between the equator and the poles. They are less common in tropical and desert ecosystems.

These are far from California’s deadliest wildfires. Numerous major wildfires occurred in California in the early 2000′s. In 2003, wildfires in southern California destroyed thousands of homes and killed more than 20 people. In 2007, deadly wildfires forced the evacuation of about 500,000 people in San Diego County. In 2013, the so-called Rim Fire burned large areas of the Stanislaus National Forest near Yosemite National Park. Some of the largest wildfires in California history burned during the summer of 2018.

The unhealthy air quality caused by the wildfires is especially concerning, because of the pandemic (global outbreak) of the respiratory disease COVID-19. Smoke-polluted air can weaken lung function, reducing the body’s ability to fight infection.

The current round of fires was made worse by an intense heat wave baking the American Southwest. On August 16, temperatures in California’s Death Valley reached 130 °F (54.4 °C). If these measurements are confirmed, they would be the hottest surface air temperatures ever recorded on Earth.