According to the state’s first snow survey of 2025, Northern California has much more precipitation than Southern California, and that pattern may persist with climate change.
As of Thursday, there is 24 inches of snow depth in the northern Sierra Nevada, according to the California Department of Water Resources. That amounts to 9 inches of water, or 91% of average, for the Phillips Station site where the survey was done. It was 37% of the April 1 average.
“We use April 1 because that’s typically when our snowpack peaks,” said Andy Reising, DWR’s water supply forecasting unit manager. Statewide, the snow water equivalent is 108% of average for this date, according to DWR’s readings from 130 electronic stations placed throughout the Sierra Nevada.
But regionally, snow measurements reveal a big difference between the northern and southern Sierras, said Reising. So far, snow in the northern region is above 160% of average for this date, thanks to a recent stream of atmospheric rivers.
“But it was less and less as we moved south through the state,” he said. “The central Sierra region is just below average, and the southern Sierra is about 75% of average. So that’s a big difference throughout the state.”
Rain was similarly uneven. Northern California has received 150% of average levels. Precipitation is slightly below average in the central region of the state and well below average in the south, he said.
Conditions can change quickly, however. Last January, the statewide snowpack measured only 28% yet ended the year slightly higher than average, said Reising. In the drought year of 2013, statewide snowpack on Jan. 2 was 137%, but ended up at just 46% of the April 1 average.
The Phillips Station is one of more than 260 snow measurement sites across the Sierra Nevada that are manually measured each winter and early spring. Data collected from the monthly snow surveys help determine the amount of water that will melt and run off to state reservoirs during warmer months.
Most years, the Sierra snowpack supplies about 30% of California’s water needs. Its natural ability to store water is why the Sierra snowpack is often referred to as California’s “frozen reservoir.”
In drought years, groundwater accounts for almost 60% of the state’s water supply. Multiple dry and drought years over recent decades have put a strain on California’s groundwater resources. Currently, groundwater monitoring wells are 31% below average, while the state’s major surface water reservoir levels are above 122%.
Bay Area reservoirs are doing well. The Sonoma Reservoir is at 70% of capacity and the San Luis Reservoir in the Santa Clara Valley is at 69% capacity.
“While our snowpack looks good now, we have a long way until April when our water supply picture will be more complete,” said DWR director Karla Nemeth. “Extreme shifts between dry and wet conditions are continuing this winter and if the past several years are any indication, anything could happen between now and April and we need to be prepared.”
State climatologist Michael Anderson said global warming may bring more extremes between the northern and southern parts of the state.
“Our bigger storms get bigger and sometimes not by a little bit. We really can have some very strong storms,” said Anderson. “With a more amplified storminess pattern, comes a more amplified pattern of warm and cold air. You can end up with extreme snowpacks, as well as extreme rainfall totals.”
“As you warm the atmosphere, you give it more energy. It can make that cold air push stronger, push further south. No longer stopping, say in Oklahoma. Pushing right on into Texas and sometimes all the way down into Mexico. So those amplified motions are what we would expect as we continue to see warming in the atmosphere,” said Anderson.
For now, the immediate forecast is dry, save a little bit of precipitation Friday in the northern half of the state. Most of the storms predicted are going to be north of California for the next two weeks.
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