2018 Total System Electric Generation

Temperatures, Precipitation, and Wildfires

California’s wide variety of climate and weather systems also play a large role in how the various generation resources shape the annual power mix. In 2018, California’s average temperature was the fourth warmest since 1895. Many cities and areas had above-average temperatures including Fresno, Los Angeles, Sacramento, San Diego, and San Francisco, with Los Angeles and San Diego having their 5th and 6th warmest year since 1946, respectively. Contributing to the national trend, the average annual temperature across the contiguous U.S. continued on its warming trend as temperatures were 1.5° Fahrenheit warmer than 2017, the 22nd consecutive year with above-average temperatures.

Total precipitation for 2018 across the contiguous U.S. was 4.6 inches above average, resulting in the wettest of the past 35 years. The national average was driven by extreme weather events on the East Coast with nine states experiencing record amounts of precipitation. California, however, differed from the East Coast as drought conditions continued in Southern California with above-average temperatures and below-normal precipitation. Northern California also began 2018 with warmer temperatures and below-normal snowpack conditions, but late-spring storms, referred to as atmospheric-rivers, aided the region’s precipitation totals.

Atmospheric rivers are long, narrow bands of moisture from the tropics that fuel enormous, rain-making storms. On average, California receives about 75 percent of its annual precipitation from November through March with these atmospheric rivers providing up to half of the state’s annual precipitation and almost 40 percent of the Sierra Nevada snowpack. However, snowpack readings measured on April 1, 2018 were still only 58 percent of average for the 2018 water year. The December-February period was the fifth driest period on record for the Sacramento watershed, a period that should normally be the wettest time of year.

California’s drought years of 2012 through 2016 created very dry vegetation conditions which were followed by an above-average wet year in 2017. This encouraged the rapid growth of grasses and underbrush that eventually became fuel for record-setting fires in the latter half of 2017; records that would be topped by even more destructive wildfires in 2018 as dryer conditions returned to the state.

The Mendocino Complex Fire in July 2018 consumed more than 450,000 acres, dwarfing the previous record-setting Thomas Fire’s 280,000 acres just six months earlier. The Mendocino Complex Fire covered some 700 square miles and burned 280 structures in Colusa, Glenn, Lake, and Mendocino counties. Also in July, the Carr Fire in Shasta and Trinity counties covered almost 230,000 acres, largely destroying the town of Keswick and more than 1,600 structures. California’s most destructive fire came in November as the Camp Fire in Butte County extended across more than 150,000 acres. The Camp Fire would end up destroying the town of Paradise, resulting in 85 deaths and the loss of more than 18,000 structures.

The Camp Fire impacted air quality in surrounding regions as smoke spread across the Central Valley. The Sacramento Metropolitan Air Quality Management District recorded 13 consecutive unhealthy Spare-the-Air days. Air quality readings of PM 2.5 levels reached a peak of 314 for the 24-hour period of Thursday, November 15, 2018, the second highest since 2003. Readings of PM 2.5 across multiple areas of Sacramento topped 400 in the overnight hours due to low inversion layers, light winds, and cool temperatures.