(CNN)Thanks to multiple atmospheric river events, average snowpack in California has gone from 18% to 98% in just two weeks.
"Increases in snowpack of this size are not common, but also not unprecedented," Julie Kalansky, deputy director of operations for the Center for Western Weather and Water Extremes (CW3E), explained.
Kalansky pointed out previous studies have shown a jump on this scale can happen about twice every three years, but usually over the course of an entire winter, not just the month of December.
While they don't have the exact rankings for each month of the year, "most of the storm events in the study we referenced for the above calculation were in the second half of December and later into the season," Kalansky added.
The sudden change gives California its wettest start to the Water Year in more than 40 years, thanks to several drought-denting rain and snow systems pushing through the area in recent weeks. The Water Year runs from October 1 through September 30 of the following year.
Parts of California are known for whiplash weather, but the rapid changes are quite remarkable given the snowpack was off to such a rough start, after a very warm and dry November for much of the state.
Northern California is doing a little better in terms of its water year, compared to where it was last year. While not at record levels, the National Weather Service (NWS) office in Sacramento tweeted the Northern Sierra precipitation is above average for this time of year, and exceptionally better than the same time last year.
However, Southern California was only able to take advantage of one of the larger atmospheric river systems recently.
"The Tuesday storm that brought 1 to 2 inches of rain to the coastal and valley areas put a dent in our rainfall deficit," the NWS office in San Diego said last week.
The area was so far behind prior to last week's storm, the recent rainfall only brought the region back to where it normally should be at this time of year, rather than ahead.
California is just one state in the West, and not all states are equal in terms of moisture received by recent storms.
"While stormy weather in December increased snowpack in California, snow water equivalent is at record lows in some stations in NM, CO, UT, MT, WY, NV," the National Integrated Drought Information System (NIDIS) said in a tweet.
The Sierras can collect a lot of the moisture from big storms, but block it from entering neighboring states.
A US Department of Agriculture snow mapping tool showed while some areas of California, Oregon, Washington, Nevada, and Arizona have relatively high snow water equivalent percentages, other states such as Colorado, New Mexico, and Wyoming are struggling, compared to average totals.