The long-term average amount of water in the state’s snowpack is about 28 inches. This snow-water content has been variable, ranging from a high of about 240 percent of the average in 1952 to a record low of 5 percent in 2015.

California’s snowpack accumulates from October to March in the Sierra Nevada and the southern Cascade Mountains. The snowpack supplies water needed for domestic and agricultural uses, hydroelectric production, winter recreation and tourism, and ecosystems. The amount of liquid water in the snowpack is referred to as snow-water content. For more information, download the Snow-water Content chapter.

The graph shows the amount of water contained in snowpack each year as a percentage of the 1991-2020 average. Measurements are taken around April 1 each year, when the snowpack has historically been the deepest.

• Since 1950, statewide snow-water content has been highly variable, ranging from more than 200 percent of average in 1952, 1969, and 1983, to 5 percent in 2015 during the multi-year drought (2012 to 2016). (Average snow-water content is about 28 inches on April 1, based on the water years 1991-2020.)
• The past decade included years that recorded among the lowest (2013, 2014, 2015) and the highest (2011, 2017, 2019) measurements. In 2021, snow-water content was 62 percent of the 1991-2020 average.

Snow remaining on the ground on April 1, 2022 at Phillips Station in the Sierra Nevada Mountains. Measurements taken near the first of the month from January to May at this and at over 260 other locations are used to forecast the amount of water that will be released as snowmelt later in the year. The most important measurement is taken around April 1, when the snowpack has historically been deepest.

Credit: Ken James/California Department of Water Resources

• The Sierra Nevada snowpack has historically provided approximately 15 million acre-feet of water, or about a third of California’s water supply.
• Monitoring the snowpack is key to managing the state’s reservoirs to minimize flood risks in the winter, and to ensure sufficient supply the rest of the year.
• Long-term monitoring of snow-water content can inform how California’s water management practices, which were designed based on historical climatic conditions, must adapt to a changing climate.

• Winter and spring precipitation, air temperature, and elevation affect snow-water content. As air temperatures warm, more precipitation falls as rain instead of snow, resulting in less snowpack. 
• A lack of winter precipitation or warm temperatures can lead to anomalously low snow-water content, referred to as “snow drought.” Consecutive snow drought years, which currently occur in the western United States at about 7 percent of the time, are projected to become more frequent in the mid-21st century.

• California Department of Water Resources, Snow surveys
• California Department of Water Resources, California Data Exchange Center – Snow