The 1997 California New Years Floods resulted from a series of winter storms, from December 26 to January 3 of 1997, fed with tropical moisture by an atmospheric river.

Similarly to the 1862 event, the flooding was a combined effect of heavy rainfall and excessive snowmelt of the relatively large early-season Sierra Nevada snowpack.

[3] The resulting flooding in the Central Valley and other low-lying areas forced over 120,000 people from their homes and caused over $2 billion in property damage alone.

This and an upper-level jet extension with peak wind speeds of 180 knots in the Western Pacific ultimately contributed to the influx of tropical moisture into California.

[3] The combination of slow-moving weather systems and strong winds brought warm, moist air into Northern California, causing prolonged and heavy rainfall.

[4] During the December 26 to January 3 storm period, the North Coast river basins, despite their lower elevations, received significant precipitation ranging from 10 to 25 inches.

[3] During the event, runoff from the Sierra Nevada basins that drain into the Central Valley was significantly increased by rain at higher elevations and melting snow.

The New Year's Day storm tested the Sacramento-Feather River flood control system, which had to manage local runoff and reservoir releases to maintain its integrity.

Prior to the major storms, reservoirs were able to reduce storage and regain flood reservation space based on forecasts and operations.

As a result, the Tuolumne River at Modesto reached a record stage height of 71.21 feet and a near-record flow of 55,800 cfs on January 4.

San Joaquin River at Vernalis reached a record peak stage height of 34.88 feet and a near-record flow of 75,600 cfs on January 5.

Consequently, the snowpack in the northern Sierra Nevada was only 60% of the average by April 1, and many major reservoirs in California did not fill to capacity from the spring snowmelt.