Overview:  La Niña events have are defined from the Oceanic Niño Index (ONI) into Weak, Moderate Strong events.   Then the seasonal (July 1 through June 30) percent of normal precipitation for each category, plus a collective category of "all" cool events, was collated for a number of cities and geographic areas. These include three major watersheds, the Northern Sierra Nevada Eight Station Index (8SI, map), the Southern Sierra Nevada Five Station Index (5SI, map) and the Tulare Basin Six Station Index (6SI, map). Additionally the seven NCDC climate division (see map) and the entire state of California (CA) averages were compared to the ENSO events.  These comparisons was done in terms of both average seasonal precipitation and also the number of occurrences within percent of normal categories.

Observations:  The best wet "signal" associated with cool ENSO (La Niña) events is, surprisingly, with the "Moderate" events, which statewide were wetter than those in the "Weak" or "Strong" categories.  Overall, there has been a strong bias toward below normal precipiation in the southern half of the state during past La NIña events. For example, Climate Divison 6, the South Coast, below normal for 20 of 22 previous La Niñas, with 13 of those showing less than 80% of normal rainfall. However, two years were between 120% and 140% of normal; one of those being 2016-17.

Also:  United States La Niña Winter Precipitation & Temperature Climatology or a graphical display of ENSO events for the entire United States from 1950-51 through 2017-2018.

Important Caveat:  The data presented here is a climatology of past events and is made up of a broad range of events from a small sample that are averaged together.  Consequently, like all averages, this type of data should not be used as a forecast! 

California La Niña Precipiation Climatology

				Table 1.  All La Niña Events - Average Percent of Normal Seasonal Precipitation (22 events)
	ENSO Type	Div. 1	Div. 2	Div. 3	Div. 4	Div. 5	Div. 6	Div. 7	CA	8SI	5SI	6SI	SF	SJC	EKA	RDD	SAC	FAT	LAX	SAN
	All La NIña	100%	96%	100%	88%	91%	79%	77%	92%	98%	94%	90%	88%	84%	103%	98%	92%	87%	82%	74%
	Weak La NIña	95%	94%	99%	87%	92%	79%	82%	90%	96%	97%	90%	87%	87%	101%	94%	92%	84%	82%	77%
	Moderate La NIña	114%	106%	112%	94%	93%	75%	62%	101%	106%	92%	92%	90%	92%	111%	112%	98%	89%	83%	63%
	Strong La NIña	100%	93%	94%	85%	88%	81%	76%	91%	97%	91%	90%	88%	76%	102%	95%	88%	91%	81%	75%
	All La NIña			Table 2.  All La Niña - Years by Percent of Normal Categories (22 events)
	% of Normal	Div. 1	Div. 2	Div. 3	Div. 4	Div. 5	Div. 6	Div. 7	CA	8SI	5SI	6SI	SF	SJC	EKA	RDD	SAC	FAT	LAX	SAN
	<80%	6	9	7	10	10	13	15	10	8	10	9	10	8	2	8	8	12	10	14
	80-100%	5	4	5	6	5	7	4	4	3	3	8	5	8	9	4	7	5	8	5
	100-120%	7	4	4	4	3	0	1	4	6	4	2	5	5	6	4	3	2	1	1
	120-140%	2	4	4	1	3	2	2	4	2	3	1	1	0	3	4	3	1	3	2
	>140%	2	1	2	1	1	0	0	0	3	2	2	1	1	2	2	1	2	0	0
	Weak La NIña			Table 3.  Weak La Niña - Years by Percent of Normal Categories (11 events)
	% of Normal	Div. 1	Div. 2	Div. 3	Div. 4	Div. 5	Div. 6	Div. 7	CA	8SI	5SI	6SI	SF	SJC	EKA	RDD	SAC	FAT	LAX	SAN
	<80%	5	5	4	5	5	5	5	5	4	4	3	4	3	2	4	3	5	4	4
	80-100%	1	1	1	3	2	4	3	2	2	1	4	4	5	4	1	5	3	4	4
	100-120%	3	2	3	1	1	0	0	1	2	2	2	0	1	1	2	0	0	0	1
	120-140%	1	1	1	0	1	1	2	2	0	2	0	1	0	1	3	1	1	2	1
	>140%	1	1	1	1	1	0	0	0	2	1	1	1	1	2	0	1	1	0	0
	Moderate La NIña			Table 4.  Moderate La Niña - Years by Percent of Normal Categories (4 events)
	% of Normal	Div. 1	Div. 2	Div. 3	Div. 4	Div. 5	Div. 6	Div. 7	CA	8SI	5SI	6SI	SF	SJC	EKA	RDD	SAC	FAT	LAX	SAN
	<80%	0	1	1	1	1	3	4	1	1	2	2	2	1	0	1	1	2	1	4
	80-100%	1	0	0	1	1	1	0	0	0	0	1	0	1	0	0	1	1	2	0
	100-120%	2	2	0	2	1	0	0	2	2	1	0	2	2	4	1	1	1	1	0
	120-140%	1	1	3	0	1	0	0	1	1	1	1	0	0	0	1	1	0	0	0
	>140%	0	0	0	0	0	0	0	0	0	0	0	0	0	0	1	0	0	0	0
	Strong La NIña			Table 5.  Strong La Niña - Years by Percent of Normal Categories (7 events)
	% of Normal	Div. 1	Div. 2	Div. 3	Div. 4	Div. 5	Div. 6	Div. 7	CA	8SI	5SI	6SI	SF	SJC	EKA	RDD	SAC	FAT	LAX	SAN
	<80%	1	2	2	3	3	4	5	3	2	3	3	3	3	0	2	4	4	4	5
	80-100%	3	3	3	2	2	2	1	2	1	2	3	1	2	4	3	0	1	2	1
	100-120%	2	0	1	1	1	0	1	1	2	1	0	3	2	1	1	2	1	0	0
	120-140%	0	2	0	1	1	1	0	1	1	0	0	0	0	2	0	1	0	1	1
	>140%	1	0	1	0	0	0	0	0	1	1	1	0	0	0	1	0	1	0	0
Table 6. Percent of Normal (1981-2010) Rainfall for All Years
	Normal	49.77"	36.69"	20.46"	22.03"	20.70"	17.80"	6.35"	24.10"	54.52	42.57	30.50	23.65"	18.42	40.33"	34.62	18.52"	11.50"	14.93"	10.34
ENSO Type	Rainfall Season	Div. 1	Div. 2	Div. 3	Div. 4	Div. 5	Div. 6	Div. 7	Calif	8SI	5SI	6SI	SF	SJC	EKA	RDD	SAC	FAT	LAX	SAN
	1950-1951	111%	109%	117%	86%	106%	57%	62%	99%	119%	119%	118%	101%	88%	115%	116%	95%	90%	55%	62%
Mod. El Niño	1951-1952	123%	129%	133%	135%	135%	162%	147%	134%	132%	123%	148%	138%	127%	118%	140%	129%	121%	176%	189%
Weak El Niño	1952-1953	118%	102%	98%	80%	82%	75%	75%	96%	100%	75%	88%	89%	62%	118%	127%	88%	84%	63%	68%
Weak El Niño	1953-1954	107%	89%	78%	78%	82%	91%	77%	89%	92%	81%	86%	60%	65%	105%	106%	73%	77%	80%	95%
Weak La Niña	1954-1955	68%	69%	62%	80%	77%	79%	71%	71%	68%	67%	77%	67%	76%	83%	75%	81%	89%	80%	75%
Mod. La Niña	1955-1956	139%	134%	142%	120%	125%	84%	76%	125%	136%	136%	125%	115%	116%	115%	143%	138%	117%	107%	47%
	1956-1957	90%	81%	93%	74%	79%	77%	65%	83%	83%	78%	75%	64%	65%	91%	81%	74%	71%	64%	93%
Stg. El Niño	1957-1958	153%	142%	128%	161%	143%	160%	126%	147%	134%	124%	137%	154%	141%	121%	179%	155%	165%	142%	145%
Weak El Niño	1958-1959	77%	68%	73%	61%	59%	53%	59%	67%	71%	61%	48%	44%	63%	81%	66%	59%	60%	37%	55%
	1959-1960	86%	78%	70%	66%	68%	69%	82%	75%	81%	70%	70%	65%	67%	86%	104%	71%	70%	55%	78%
	1960-1961	97%	78%	73%	59%	61%	42%	52%	72%	72%	56%	50%	59%	64%	110%	93%	68%	60%	32%	36%
	1961-1962	82%	86%	100%	97%	101%	121%	89%	95%	84%	97%	97%	75%	80%	72%	99%	94%	99%	126%	100%
	1962-1963	116%	116%	131%	110%	105%	61%	58%	108%	118%	105%	98%	94%	130%	109%	114%	136%	101%	56%	41%
Mod. El Niño	1963-1964	78%	68%	85%	62%	71%	71%	79%	73%	67%	71%	70%	52%	18%	93%	57%	67%	59%	53%	73%
Weak La Niña	1964-1965	117%	112%	120%	96%	108%	82%	70%	107%	117%	123%	104%	94%	97%	101%	115%	99%	97%	92%	89%
Stg. El Niño	1965-1966	88%	71%	79%	75%	73%	97%	109%	81%	71%	75%	63%	69%	68%	80%	90%	57%	53%	137%	157%
	1966-1967	109%	123%	140%	135%	138%	129%	90%	125%	117%	134%	163%	124%	129%	110%	131%	142%	130%	147%	111%
	1967-1968	79%	76%	78%	63%	67%	77%	96%	75%	71%	59%	60%	61%	84%	70%	69%	64%	63%	111%	83%
Mod. El Niño	1968-1969	120%	128%	147%	161%	169%	175%	142%	145%	127%	163%	186%	106%	136%	118%	151%	130%	200%	184%	121%
Weak El Niño	1969-1970	111%	113%	115%	80%	86%	63%	69%	97%	111%	97%	79%	88%	73%	95%	154%	93%	79%	52%	66%
Mod. La Niña	1970-1971	119%	106%	125%	85%	85%	80%	64%	102%	104%	76%	76%	79%	95%	119%	133%	88%	74%	83%	83%
Weak La Niña	1971-1972	93%	68%	82%	48%	57%	51%	49%	69%	66%	67%	54%	47%	41%	98%	75%	50%	46%	48%	59%
Stg. El Niño	1972-1973	95%	110%	104%	144%	122%	129%	113%	114%	96%	95%	128%	145%	150%	86%	123%	136%	121%	142%	119%
Stg. La Niña	1973-1974	149%	132%	108%	116%	105%	87%	74%	120%	143%	110%	101%	117%	104%	132%	161%	112%	91%	100%	69%
Weak La Niña	1974-1975	104%	92%	102%	92%	94%	93%	74%	96%	93%	105%	95%	77%	87%	99%	129%	86%	67%	96%	111%
Stg. La Niña	1975-1976	67%	49%	56%	39%	54%	63%	78%	56%	48%	55%	54%	34%	37%	83%	63%	36%	71%	48%	95%
Weak El Niño	1976-1977	41%	41%	68%	50%	50%	66%	84%	52%	37%	45%	54%	47%	58%	44%	58%	38%	66%	82%	84%
Weak El Niño	1977-1978	127%	131%	124%	157%	157%	207%	200%	147%	132%	148%	155%	114%	141%	90%	179%	142%	158%	224%	195%
	1978-1979	74%	80%	80%	91%	99%	131%	129%	90%	77%	101%	90%	79%	78%	62%	95%	97%	93%	132%	162%
Weak El Niño	1979-1980	110%	118%	133%	121%	128%	165%	180%	128%	111%	134%	136%	104%	121%	94%	109%	128%	104%	181%	164%
	1980-1981	73%	74%	79%	70%	73%	69%	71%	73%	69%	64%	67%	65%	71%	73%	95%	68%	72%	60%	84%
	1981-1982	142%	145%	148%	132%	140%	100%	103%	135%	153%	152%	126%	157%	98%	120%	156%	164%	97%	72%	120%
V. Stg. El Niño	1982-1983	162%	166%	164%	193%	186%	199%	191%	176%	166%	187%	194%	161%	194%	147%	184%	192%	205%	209%	190%
Weak La Niña	1983-1984	111%	108%	120%	78%	94%	64%	88%	99%	110%	109%	95%	95%	86%	120%	105%	78%	66%	70%	60%
Weak La Niña	1984-1985	78%	71%	78%	75%	77%	78%	125%	78%	66%	72%	86%	85%	81%	87%	75%	58%	69%	86%	100%
	1985-1986	114%	126%	139%	122%	133%	116%	111%	124%	131%	139%	142%	121%	120%	97%	133%	128%	129%	120%	147%
Mod. El Niño	1986-1987	72%	62%	67%	60%	63%	61%	82%	65%	61%	56%	61%	59%	50%	69%	63%	56%	81%	51%	100%
Stg. El Niño	1987-1988	77%	73%	64%	73%	73%	99%	115%	77%	65%	63%	73%	75%	72%	80%	84%	75%	70%	84%	137%
Stg. La Niña	1988-1989	88%	86%	97%	60%	71%	57%	64%	79%	86%	71%	79%	74%	53%	86%	93%	77%	76%	54%	59%
	1989-1990	74%	74%	78%	58%	68%	52%	43%	68%	72%	72%	66%	61%	64%	67%	83%	96%	82%	49%	82%
	1990-1991	64%	69%	80%	80%	79%	99%	107%	77%	61%	76%	78%	60%	76%	62%	61%	69%	85%	77%	123%
Stg. El Niño	1991-1992	68%	71%	63%	92%	78%	124%	155%	82%	67%	64%	65%	81%	104%	54%	79%	71%	96%	141%	135%
	1992-1993	120%	128%	127%	139%	134%	188%	185%	137%	121%	134%	132%	113%	137%	108%	146%	138%	144%	183%	191%
	1993-1994	63%	64%	67%	70%	67%	78%	57%	67%	59%	55%	68%	64%	79%	73%	65%	65%	74%	54%	103%
Mod. El Niño	1994-1995	143%	163%	166%	161%	164%	182%	149%	161%	159%	169%	153%	144%	152%	128%	158%	127%	165%	163%	178%
Mod. La Niña	1995-1996	118%	115%	129%	105%	106%	76%	51%	109%	112%	104%	102%	105%	112%	111%	107%	102%	95%	83%	53%
	1996-1997	118%	115%	135%	112%	119%	87%	66%	114%	126%	129%	114%	96%	99%	125%	76%	107%	104%	83%	73%
V. Stg. El Niño	1997-1998	154%	160%	132%	191%	168%	211%	177%	167%	154%	154%	179%	200%	186%	145%	181%	174%	175%	208%	185%
Stg. La Niña	1998-1999	109%	96%	101%	81%	85%	65%	64%	92%	103%	92%	79%	99%	88%	124%	85%	75%	61%	61%	70%
Stg. La Niña	1999-2000	95%	98%	86%	101%	97%	78%	64%	92%	103%	99%	92%	105%	80%	90%	95%	116%	112%	77%	60%
Weak La Niña	2000-2001	59%	66%	58%	90%	81%	100%	93%	74%	63%	71%	75%	82%	88%	57%	83%	81%	92%	120%	89%
	2001-2002	93%	87%	76%	73%	77%	36%	32%	76%	87%	81%	84%	106%	72%	101%	80%	97%	61%	30%	31%
Mod. El Niño	2002-2003	117%	105%	91%	99%	94%	105%	90%	103%	108%	91%	104%	101%	99%	132%	97%	90%	85%	110%	111%
	2003-2004	94%	91%	83%	76%	74%	60%	93%	83%	90%	71%	69%	87%	88%	95%	100%	71%	66%	62%	54%
Weak El Niño	2004-2005	101%	110%	115%	144%	139%	192%	206%	130%	107%	129%	127%	135%	161%	110%	107%	118%	138%	249%	234%
Weak La Niña	2005-2006	139%	141%	135%	121%	127%	93%	84%	127%	150%	132%	119%	146%	147%	146%	125%	127%	127%	88%	56%
Weak El Niño	2006-2007	75%	62%	56%	50%	53%	31%	32%	57%	67%	59%	56%	71%	58%	88%	63%	59%	52%	22%	40%
Stg. La Niña	2007-2008	81%	72%	75%	79%	72%	88%	82%	78%	67%	69%	85%	73%	71%	85%	66%	74%	73%	91%	76%
Weak La Niña	2008-2009	70%	78%	76%	70%	76%	68%	78%	73%	86%	94%	85%	77%	74%	74%	66%	88%	68%	61%	95%
Mod. El Niño	2009-2010	99%	97%	93%	115%	105%	114%	113%	103%	99%	107%	113%	102%	110%	110%	84%	112%	107%	110%	110%
Stg. La Niña	2010-2011	112%	123%	143%	125%	141%	139%	109%	127%	135%	154%	149%	122%	100%	112%	101%	129%	152%	135%	131%
Mod. La Niña	2011-2012	82%	73%	60%	68%	63%	64%	59%	70%	78%	61%	73%	66%	46%	101%	65%	66%	71%	58%	84%
	2012-2013	77%	78%	79%	60%	61%	47%	65%	69%	80%	63%	51%	70%	61%	80%	79%	82%	49%	39%	68%
	2013-2014	55%	58%	66%	44%	48%	43%	63%	54%	56%	47%	49%	0.5302	41%	52%	49%	53%	42%	41%	53%
Weak El Niño	2014-2015	82%	78%	83%	35%	59%	60%	83%	75%	71%	45%	43%	0.7691	88%	84%	73%	86%	57%	57%	94%
V. Stg. El Niño	2015-2016	111%	106%	116%	97%	102%	67%	89%	98%	99%	99%	89%	0.9797	96%	120%	114%	88%	129%	65%	113%
Weak La Niña	2016-2017	141%	157%	178%	150%	155%	131%	122%	141%	175%	171%	154%	1.3687	118%	157%	130%	179%	150%	127%	135%
Weak La Niña	2017-2018	70%	78%	96%	66%	72%	45%	51%	67%	76%	72%	60%	72%	59%	94%	56%	86%	60%	32%	33%
ENSO Type	Rainfall Season	Div. 1	Div. 2	Div. 3	Div. 4	Div. 5	Div. 6	Div. 7	Calif	8SI	5SI	6SI	SF	SJC	EKA	RDD	SAC	FAT	LAX	SAN

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