California El Nino and La Nina Precipitation Climnatology

This is a catalog of California precipitation anomalies for previous La Niña events based upon their strength and the 10 state hydrologic regions and the 3 Sierra Nevada Precipitation Indices. It has the average for all events, weak events, moderate events, and strong events and the wide range of the individual seasons that went into making up each of the averages. (For El Niño click HERE).

It cannot be stressed strongly enough that this is a climatological analysis and NOT a forecasting tool. This is especially true for the averages of different strength events which are made up of what are a very broad range of conditions; some that are decidedly atypical.

The Relative Oceanic Niño Index (RONI) is used to identify El Niño (warm) and La Niña (cool) events in the tropical Pacific. The RONI is the running 3-month mean SST anomaly for the Niño 3.4 region (i.e., 5°N-5°S, 120°-170°W) minus the overall average tropical 3-month sea surface temperature anomaly (SSTA). Events are defined as 5 consecutive overlapping 3-month periods at or above the +0.5^o anomaly for warm (El Niño) events and at or below the -0.5 anomaly for cool (La Niña) events. The threshold is further broken down into Weak (with a 0.5 to 0.9 SST anomaly), Moderate (1.0 to 1.4), Strong (1.5 to 1.9) and Very Strong (≥ 2.0) events. For the purpose of this report, an event is categorized as weak, moderate, strong or very strong it must have equaled or exceeded the threshold of the highest category for at least 3 consecutive overlapping 3-month periods.

El Niño Events:
     Weak: 1954-1955, 1964-1965, 1970-1971, 1974-1975, 1983-1984, 1984-1985, 1995-1996, 2000-2001, 2005-2006, 2008-2009, 2011-2012, 2024-2025
     Moderate: 1955-1956, 2016-2017, 2017-2018, 2020-2021, 2021-2022, 2022-2023
     Strong: 1973-1974, 1975-1976, 1988-1989, 1998-1999, 1999-2000, 2007-2008, 2010-2011

		Table 1. All La Niña Events - Average Percent of Normal Seasonal Precipitation (25 events)
ENSO Type	N Coast	Sacramento	N Lahontan	SF Bay	S Joaquin	C Coast	Tulare Lk	S Lahontan	S Coast	Colo River	Calif	8SI	5SI	6SI
All La NIña	103%	100%	105%	97%	100%	92%	96%	87%	84%	79%	96%	101%	100%	99%
Weak La NIña	103%	98%	98%	95%	96%	87%	92%	86%	80%	84%	94%	98%	96%	95%
Moderate La NIña	103%	105%	126%	109%	115%	105%	108%	91%	91%	73%	102%	107%	112%	108%
Strong La NIña	105%	98%	98%	91%	95%	90%	94%	85%	84%	77%	95%	100%	98%	98%

All La NIña		Table 2. All La Niña - Years by Percent of Normal Categories (25 events)
% of Normal	N Coast	Sacramento	N Lahontan	SF Bay	S Joaquin	C Coast	Tulare Lk	S Lahontan	S Coast	Colo River	Calif	8SI	5SI	6SI
<80%	7	9	6	9	10	10	9	14	13	14	9	9	11	6
80-100%	5	3	6	7	4	5	8	5	9	6	6	3	3	9
100-120%	5	6	6	2	5	7	3	2	0	2	4	7	5	5
120-140%	4	4	3	4	3	1	2	2	1	1	5	3	1	2
>140%	4	3	4	3	3	2	3	2	2	2	1	3	5	3
Max % Normal	156%	164%	188%	168%	178%	185%	185%	160%	181%	162%	155%	179%	181%	187%
Min % Normal	57%	44%	55%	39%	50%	46%	44%	31%	40%	26%	47%	44%	46%	34%

Weak La NIña		Table 3. Weak La Niña - Years by Percent of Normal Categories (12 events)
% of Normal	N Coast	Sacramento	N Lahontan	SF Bay	S Joaquin	C Coast	Tulare Lk	S Lahontan	S Coast	Colo River	Calif	8SI	5SI	6SI
<80%	3	4	3	4	5	5	3	6	6	6	4	4	5	2
80-100%	2	2	3	5	2	3	6	3	6	4	3	2	2	5
100-120%	2	4	3	1	3	4	2	2	0	0	4	5	3	4
120-140%	4	1	3	1	2	0	1	1	0	0	1	0	1	1
>140%	1	1	0	1	0	0	0	0	0	2	0	1	1	0
Max % Normal	140%	144%	137%	141%	136%	117%	129%	138%	96%	162%	130%	153%	142%	129%
Min % Normal	60%	68%	55%	71%	65%	64%	69%	49%	52%	36%	73%	64%	65%	78%

Moderate La NIña		Table 4. Moderate La Niña - Years by Percent of Normal Categories (6 events)
% of Normal	N Coast	Sacramento	N Lahontan	SF Bay	S Joaquin	C Coast	Tulare Lk	S Lahontan	S Coast	Colo River	Calif	8SI	5SI	6SI
<80%	3	3	1	2	2	3	3	3	3	4	3	3	3	3
80-100%	0	0	1	1	1	0	0	1	1	0	0	0	0	0
100-120%	1	0	1	0	0	1	0	0	0	1	0	0	0	0
120-140%	0	2	0	1	1	0	1	0	1	1	2	2	0	1
>140%	2	1	3	2	2	2	2	2	1	0	1	1	3	2
Max % Normal	156%	164%	188%	168%	178%	185%	185%	160%	181%	127%	155%	179%	181%	187%
Min % Normal	57%	44%	59%	39%	50%	51%	44%	31%	40%	26%	47%	44%	46%	34%

Strong La NIña		Table 5. Strong La Niña - Years by Percent of Normal Categories (7 events)
% of Normal	N Coast	Sacramento	N Lahontan	SF Bay	S Joaquin	C Coast	Tulare Lk	S Lahontan	S Coast	Colo River	Calif	8SI	5SI	6SI
<80%	1	2	2	3	3	2	3	5	4	4	2	2	3	1
80-100%	3	1	2	1	1	2	2	1	2	2	3	1	1	4
100-120%	2	2	2	1	2	2	1	0	0	1	0	2	2	1
120-140%	0	1	0	2	0	1	0	1	0	0	2	1	0	0
>140%	1	1	1	0	1	0	1	0	1	0	0	1	1	1
Max % Normal	156%	140%	144%	129%	152%	137%	159%	139%	147%	106%	131%	146%	163%	160%
Min % Normal	71%	52%	58%	41%	52%	46%	61%	68%	58%	60%	59%	49%	58%	58%

		Table 6. Catalog of La Niña Years (1950-1951 to 2024-2025)
Weak La Niña	N Coast	Sacramento	N Lahontan	SF Bay	S Joaquin	C Coast	Tulare Lk	S Lahontan	S Coast	Colo River	Calif	8SI	5SI	6SI
1954-1955	74%	70%	66%	74%	79%	83%	85%	72%	79%	72%	73%	69%	71%	83%
1964-1965	120%	116%	120%	106%	123%	100%	111%	92%	85%	86%	110%	119%	130%	112%
1970-1971	122%	107%	118%	97%	92%	83%	88%	77%	83%	61%	101%	107%	80%	82%
1974-1975	104%	99%	100%	97%	106%	101%	98%	90%	93%	70%	98%	95%	111%	102%
1983-1984	121%	113%	120%	98%	110%	78%	95%	105%	76%	148%	108%	112%	115%	102%
1984-1985	81%	73%	81%	83%	77%	74%	86%	138%	90%	162%	82%	67%	76%	93%
1995-1996	124%	120%	127%	126%	115%	102%	106%	72%	77%	36%	109%	115%	109%	109%
2000-2001	60%	68%	55%	76%	79%	109%	88%	96%	96%	91%	73%	64%	75%	81%
2005-2006	140%	144%	137%	141%	136%	117%	129%	106%	93%	80%	130%	153%	142%	129%
2008-2009	78%	83%	83%	80%	88%	68%	76%	80%	72%	93%	78%	88%	99%	92%
2011-2012	90%	75%	64%	71%	65%	65%	70%	56%	69%	67%	74%	79%	65%	78%
2024-2025	116%	104%	104%	89%	77%	64%	69%	49%	52%	37%	92%	106%	78%	78%

Moderate La Niña	N Coast	Sacramento	N Lahontan	SF Bay	S Joaquin	C Coast	Tulare Lk	S Lahontan	S Coast	Colo River	Calif	8SI	5SI	6SI
1955-1956	143%	138%	142%	137%	137%	116%	126%	85%	86%	69%	127%	139%	143%	135%
2016-2017	156%	164%	188%	168%	178%	146%	158%	144%	124%	127%	155%	179%	181%	165%
2017-2018	78%	80%	109%	73%	81%	64%	68%	64%	46%	41%	73%	78%	78%	66%
2020-2021	57%	44%	59%	39%	50%	51%	44%	31%	40%	26%	47%	44%	46%	34%
2021-2022	75%	77%	99%	82%	73%	69%	65%	64%	70%	54%	72%	80%	66%	59%
2022-2023	107%	128%	159%	157%	170%	185%	185%	160%	181%	119%	138%	124%	161%	187%

Strong La Niña	N Coast	Sacramento	N Lahontan	SF Bay	S Joaquin	C Coast	Tulare Lk	S Lahontan	S Coast	Colo River	Calif	8SI	5SI	6SI
1973-1974	156%	140%	112%	129%	115%	113%	105%	74%	84%	63%	125%	146%	116%	109%
1975-1976	71%	52%	58%	41%	52%	46%	61%	72%	66%	86%	59%	49%	58%	58%
1988-1989	93%	90%	97%	69%	75%	57%	76%	68%	64%	68%	81%	88%	75%	86%
1998-1999	115%	101%	111%	94%	94%	84%	85%	79%	58%	66%	96%	105%	96%	85%
1999-2000	97%	102%	88%	103%	106%	106%	97%	76%	74%	60%	94%	105%	104%	99%
2007-2008	86%	74%	75%	78%	75%	88%	78%	87%	95%	90%	79%	68%	72%	91%
2010-2011	120%	130%	144%	124%	152%	137%	159%	139%	147%	106%	131%	137%	163%	160%