Snowfall Explorer

Pick a climate-driver state and see every Mammoth or Central Sierra Snow Lab season that matched it — or flip it around and see what the snowiest and leanest winters had in common.

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Driver timing

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Driver state

Pick any states of a driver to combine them (Weak or Moderate Niña); seasons must match every driver you set. Driver timing sets the months each driver is averaged over — except ENSO event peak and IOD, which always use their own.

Slow forcings

ENSO (RONI)now +1.69 · JAS

Relative Niño 3.4 averaged over the driver window. ±0.5 °C = event, ±1.0 moderate, ±1.5 strong.

ENSO event peak

The event's strongest 3-month RONI, however the season averaged out — how 'a weak La Niña year' is usually meant.

PDOnow -1.55 · Sep

Sign of the Pacific Decadal Oscillation; ±1 marks a strong phase.

QBO (50 hPa)now +4.21 · Sep

Equatorial stratospheric wind at 50 hPa: easterly (−) or westerly (+); ±10 m/s is a strong phase.

IOD (DMI)now +0.57 · Sep

Indian Ocean Dipole in Sep–Nov, when it peaks, whatever the timing setting. ±0.4 °C = event, ±0.8 strong.

SOInow -2.00 · Sep

Southern Oscillation Index, ±½ SD of the window. Negative SOI goes with El Niño.

Circulation modes

Not predictable a season ahead — read these as “what the winter did,” not a forecast.

Polar vortexnow +18 · Feb

10 hPa zonal wind at 60°N, ±½ SD. A weak vortex favours cold outbreaks.

PNAnow -0.54 · Sep

Pacific/North American pattern, ±½ SD. +PNA = western ridge.

EPOnow -35 · Aug

Alaska/North Pacific height dipole, ±½ SD. −EPO = Alaska heights low relative to the North Pacific: an Alaskan ridge, or a deep low to its south.

WPOnow -0.10 · Sep

West Pacific Oscillation, ±½ SD.

AOnow +1.11 · Sep

Arctic Oscillation, ±½ SD. −AO = high-latitude blocking.

NAOnow +0.17 · Sep

North Atlantic Oscillation, ±½ SD.

Seasons

of 57 (1969-70 to 2025-26)

Average

352"

100% of all-season avg

Median

321"

Above average

24 of 57

all-season avg 352"

Mammoth Mountain · Full season snowfall

All seasons · drivers from Dec–Feb, the usual ENSO-classification season

Seasons and their drivers

Season	Snow	% avg	ENSO (RONI)	ENSO event peak	PDO	QBO (50 hPa)	IOD (DMI)	SOI	Polar vortex	PNA	EPO	WPO	AO	NAO
1969-70	245"	69%	Neut+0.46	Niño+0.81	Warm+1.07	West+12	Neut+0.36	−SOI-0.55	Weak+15	+PNA+0.63	−EPO-52	−WPO-0.55	−AO-1.81	−NAO-0.11
1970-71	256"	73%	Niña-0.93	Niña-1.00	Cool-1.23	East-19	Neut-0.33	+SOI+1.41	Weak+21	−PNA-0.33	+EPO+40	−WPO-1.18	Neut-0.46	−NAO-0.29
1971-72	269"	76%	Neut-0.19	Neut-0.41	Cool-1.95	West+13	Neut-0.24	Neut+0.62	Strong+36	−PNA-0.74	Neut+31	−WPO-0.58	+AO+0.27	Neut+0.28
1972-73	371"	105%	Niño+1.62	Niño+1.97	Cool-0.35	East-20	+IOD+1.42	−SOI-0.99	Weak+22	Neut-0.06	Neut-2.66	+WPO+0.76	+AO+1.06	Neut+0.20
1973-74	307"	87%	Niña-1.61	Niña-1.91	Cool-1.03	West+9.35	Neut-0.32	+SOI+2.10	Strong+42	−PNA-0.18	Neut+4.76	−WPO-1.25	Neut-0.13	Neut+0.31
1974-75	379"	107%	Neut-0.20	Niña-0.59	Cool-0.42	East-13	−IOD-0.78	Neut+0.15	Weak+22	Neut+0.11	+EPO+71	−WPO-0.70	+AO+0.77	+NAO+0.40
1975-76	198"	56%	Niña-0.93	Niña-1.11	Cool-1.20	West+10	−IOD-0.92	+SOI+1.73	Strong+48	−PNA-0.15	+EPO+48	−WPO-0.71	+AO+0.94	Neut+0.23
1976-77	94"	27%	Niño+0.98	Niño+1.08	Warm+1.31	East-1.12	Neut+0.06	Neut+0.13	Weak+19	+PNA+0.79	−EPO-50	−WPO-0.73	−AO-2.54	−NAO-0.53
1977-78	488"	138%	Niño+0.91	Niño+1.10	Warm+0.42	West+3.08	Neut+0.39	−SOI-1.32	Neut+27	Neut+0.27	−EPO-87	Neut-0.28	−AO-1.10	−NAO-0.35
1978-79	387"	110%	Neut+0.31	Neut+0.35	Cool-0.71	West+10	Neut-0.26	Neut+0.14	Neut+28	−PNA-0.47	+EPO+39	+WPO+0.73	−AO-1.28	−NAO-0.69
1979-80	445"	126%	Niño+0.58	Niño+0.65	Warm+0.23	East-9.37	Neut-0.00	Neut-0.01	Strong+35	Neut+0.19	−EPO-52	−WPO-0.73	Neut-0.54	Neut+0.09
1980-81	230"	65%	Neut-0.04	Neut-0.18	Warm+0.90	West+6.14	−IOD-0.69	Neut+0.04	Strong+38	+PNA+0.52	−EPO-87	−WPO-1.21	Neut-0.16	+NAO+0.41
1981-82	503"	143%	Neut+0.08	Neut+0.22	Warm+0.18	East-3.47	−IOD-0.60	+SOI+0.68	Neut+26	−PNA-0.25	−EPO-31	Neut-0.22	Neut-0.41	Neut+0.01
1982-83	546"	155%	Niño+2.31	Niño+2.40	Warm+0.49	West+5.54	+IOD+1.34	−SOI-3.08	Strong+37	+PNA+0.67	−EPO-40	Neut+0.20	Neut+0.23	+NAO+0.64
1983-84	273"	78%	Niña-0.71	Niña-1.10	Warm+1.46	East-0.76	Neut+0.01	Neut+0.35	Strong+39	+PNA+0.33	−EPO-26	−WPO-0.95	+AO+0.27	+NAO+0.53
1984-85	237"	67%	Niña-0.82	Niña-0.93	Warm+0.61	East-8.23	−IOD-0.60	Neut+0.24	Weak+18	Neut+0.04	Neut-4.89	Neut-0.35	−AO-1.22	−NAO-0.26
1985-86	434"	123%	Neut-0.25	Neut-0.27	Warm+0.93	West+6.17	Neut+0.02	Neut+0.10	Strong+38	+PNA+0.59	−EPO-85	−WPO-1.07	−AO-1.71	Neut+0.11
1986-87	196"	56%	Niño+1.41	Niño+1.46	Warm+1.55	East-0.20	Neut+0.16	−SOI-1.10	Weak+16	+PNA+0.60	Neut+18	+WPO+0.60	−AO-0.80	Neut-0.06
1987-88	230"	65%	Neut+0.46	Niño+1.34	Warm+0.55	West+3.77	+IOD+0.79	Neut-0.33	Neut+32	+PNA+0.57	+EPO+38	+WPO+1.31	Neut-0.42	+NAO+0.34
1988-89	251"	71%	Niña-1.66	Niña-1.95	Cool-0.93	West+3.03	Neut-0.27	+SOI+1.30	Strong+40	−PNA-0.14	+EPO+59	+WPO+0.37	+AO+2.57	+NAO+0.66
1989-90	214"	61%	Neut+0.22	Neut+0.32	Cool-0.58	East-7.82	Neut-0.20	−SOI-0.77	Strong+35	−PNA-0.14	+EPO+64	Neut-0.14	+AO+1.14	Neut+0.26
1990-91	242"	69%	Niño+0.51	Niño+0.57	Cool-1.72	West+7.26	Neut-0.02	Neut+0.23	Neut+28	Neut+0.10	−EPO-36	Neut-0.48	+AO+0.40	+NAO+0.47
1991-92	226"	64%	Niño+2.06	Niño+2.12	Warm+0.01	East-1.94	+IOD+0.41	−SOI-1.89	Neut+28	+PNA+0.43	Neut+31	Neut-0.04	+AO+1.06	+NAO+0.39
1992-93	473"	134%	Niño+0.53	Niño+0.70	Warm+0.02	West+2.18	−IOD-0.86	−SOI-0.73	Strong+38	−PNA-0.14	Neut+14	Neut+0.03	+AO+1.76	+NAO+0.52
1993-94	275"	78%	Neut+0.33	Neut+0.48	Warm+0.63	West+1.81	Neut-0.00	Neut+0.13	Neut+28	Neut+0.04	Neut-11	Neut+0.11	Neut-0.39	+NAO+0.59
1994-95	540"	153%	Niño+1.11	Niño+1.28	Cool-1.05	East-0.77	+IOD+1.22	−SOI-0.58	Neut+30	+PNA+0.38	−EPO-26	−WPO-0.61	+AO+0.68	+NAO+0.78
1995-96	321"	91%	Niña-0.87	Niña-1.02	Warm+0.82	West+2.63	Neut-0.27	Neut+0.27	Strong+41	Neut+0.09	−EPO-44	−WPO-0.88	−AO-1.04	−NAO-0.31
1996-97	324"	92%	Neut-0.18	Neut-0.30	Warm+0.23	East-8.12	−IOD-1.39	+SOI+1.01	Strong+35	Neut+0.04	−EPO-62	−WPO-0.66	Neut-0.16	Neut-0.01
1997-98	451"	128%	Niño+2.08	Niño+2.28	Warm+1.18	West+5.62	+IOD+1.99	−SOI-1.90	Weak+20	+PNA+0.56	Neut+5.84	+WPO+0.54	Neut-0.77	Neut-0.02
1998-99	332"	94%	Niña-1.49	Niña-1.61	Cool-0.97	East-4.92	−IOD-0.97	+SOI+1.41	Weak+20	Neut+0.10	+EPO+82	+WPO+0.70	+AO+0.63	+NAO+0.36
1999-00	383"	109%	Niña-1.46	Niña-1.56	Cool-1.81	West+7.50	Neut-0.02	+SOI+1.26	Strong+42	Neut+0.16	+EPO+67	−WPO-0.58	+AO+1.09	+NAO+0.74
2000-01	394"	112%	Niña-0.75	Niña-0.82	Warm+0.16	East-1.61	Neut-0.17	+SOI+1.15	Weak+17	+PNA+0.57	Neut+7.02	+WPO+0.40	−AO-1.29	Neut+0.01
2001-02	300"	85%	Neut-0.16	Neut-0.32	Cool-1.00	East-5.67	−IOD-0.45	Neut+0.20	Weak+16	Neut+0.11	+EPO+70	Neut+0.14	+AO+0.41	Neut+0.13
2002-03	356"	101%	Niño+0.83	Niño+1.33	Warm+1.42	West+5.37	+IOD+0.63	−SOI-0.67	Weak+24	+PNA+0.71	−EPO-61	Neut+0.19	Neut-0.65	Neut-0.01
2003-04	349"	99%	Neut+0.19	Neut+0.25	Cool-0.46	East-7.05	Neut-0.14	Neut+0.31	Weak+14	+PNA+0.41	Neut-8.54	Neut-0.07	−AO-0.94	Neut+0.06
2004-05	570"	162%	Niño+0.55	Niño+0.71	Cool-0.28	West+6.77	Neut-0.07	−SOI-1.14	Strong+42	Neut+0.14	−EPO-35	Neut-0.15	Neut+0.14	+NAO+0.55
2005-06	579"	164%	Niña-0.86	Niña-0.90	Warm+0.27	East-13	−IOD-0.76	Neut+0.62	Weak+13	+PNA+0.32	+EPO+38	Neut+0.18	−AO-0.80	Neut+0.10
2006-07	222"	63%	Niño+0.56	Niño+0.91	Cool-0.60	West+7.99	+IOD+0.94	−SOI-0.41	Neut+33	+PNA+0.50	+EPO+50	+WPO+1.08	+AO+1.04	Neut+0.25
2007-08	334"	95%	Niña-1.67	Niña-1.73	Cool-1.27	East-14	Neut+0.18	+SOI+2.02	Neut+32	Neut+0.10	+EPO+81	+WPO+0.44	+AO+0.83	+NAO+0.38
2008-09	470"	133%	Niña-0.91	Niña-0.96	Cool-1.63	West+8.09	Neut-0.05	+SOI+1.45	Weak+21	−PNA-0.27	+EPO+38	+WPO+0.88	+AO+0.28	Neut-0.06
2009-10	558"	158%	Niño+1.36	Niño+1.50	Cool-0.08	West+1.34	Neut-0.18	−SOI-1.09	Weak+24	+PNA+0.41	−EPO-108	Neut-0.14	−AO-3.27	−NAO-0.91
2010-11	669"	190%	Niña-1.40	Niña-1.63	Cool-1.78	West+6.87	−IOD-0.79	+SOI+2.63	Strong+39	−PNA-0.36	−EPO-28	−WPO-0.95	−AO-0.96	−NAO-0.39
2011-12	263"	75%	Niña-0.78	Niña-1.02	Cool-1.88	West+0.73	Neut+0.36	+SOI+1.39	Neut+25	+PNA+0.38	+EPO+89	Neut-0.35	+AO+0.66	+NAO+0.81
2012-13	308"	87%	Neut-0.46	Niña-0.57	Cool-1.27	East-10	Neut+0.24	Neut-0.30	Weak+13	Neut+0.07	+EPO+62	+WPO+0.29	−AO-1.13	Neut+0.02
2013-14	238"	68%	Neut-0.36	Neut-0.43	Cool-0.69	West+9.88	Neut+0.01	Neut+0.55	Strong+40	−PNA-0.11	−EPO-66	−WPO-0.93	Neut+0.18	+NAO+0.47
2014-15	176"	50%	Niño+0.55	Niño+0.62	Warm+1.63	East-9.69	Neut+0.04	−SOI-0.42	Neut+29	+PNA+0.33	−EPO-88	−WPO-0.55	+AO+0.81	+NAO+0.89
2015-16	362"	103%	Niño+2.07	Niño+2.25	Warm+0.77	West+5.80	+IOD+0.78	−SOI-1.59	Strong+45	+PNA+0.82	Neut+10	+WPO+1.03	Neut-0.01	+NAO+0.72
2016-17	618"	175%	Niña-0.65	Niña-0.96	Warm+0.18	West+9.40	−IOD-0.69	Neut+0.14	Neut+30	Neut+0.08	Neut-5.03	+WPO+0.48	+AO+1.01	Neut+0.32
2017-18	262"	74%	Niña-1.09	Niña-1.14	Warm+0.09	East-0.35	Neut-0.06	Neut+0.19	Neut+25	Neut+0.17	−EPO-24	+WPO+0.39	Neut-0.08	+NAO+0.67
2018-19	492"	140%	Niño+0.70	Niño+0.82	Cool-0.41	East-3.61	Neut+0.30	Neut-0.09	Weak+16	Neut+0.21	+EPO+40	+WPO+1.05	Neut+0.14	Neut+0.24
2019-20	281"	80%	Neut+0.15	Neut+0.29	Cool-0.95	West+1.95	+IOD+1.51	Neut-0.17	Strong+41	Neut+0.08	+EPO+101	+WPO+0.95	+AO+1.96	+NAO+0.71
2020-21	245"	69%	Niña-1.30	Niña-1.46	Cool-0.89	West+7.32	Neut-0.35	+SOI+1.74	Weak+19	+PNA+0.36	+EPO+67	+WPO+1.42	−AO-1.76	−NAO-0.22
2021-22	260"	74%	Niña-1.18	Niña-1.24	Cool-2.35	East-5.26	−IOD-0.70	+SOI+1.03	Strong+46	−PNA-0.10	Neut+4.34	Neut-0.45	+AO+0.81	+NAO+0.52
2022-23	715"	203%	Niña-0.85	Niña-1.10	Cool-1.70	West+7.75	−IOD-0.97	+SOI+1.64	Neut+31	−PNA-0.08	+EPO+41	+WPO+1.46	Neut-0.65	+NAO+0.40
2023-24	367"	104%	Niño+1.11	Niño+1.42	Cool-1.53	East-8.93	+IOD+1.54	Neut-0.34	Weak+21	+PNA+0.34	+EPO+48	+WPO+1.14	Neut+0.05	+NAO+0.49
2024-25	286"	81%	Niña-1.00	Niña-1.10	Cool-1.58	West+11	−IOD-0.46	Neut+0.64	Strong+48	+PNA+0.78	−EPO-36	+WPO+0.34	Neut-0.39	+NAO+0.37
2025-26	297"	84%	Niña-0.91	Niña-1.04	Cool-1.07	East-9.58	−IOD-1.23	+SOI+0.81	Neut+24	−PNA-0.21	−EPO-40	Neut+0.12	−AO-0.97	−NAO-0.10
Most over-represented vs. all 57 seasons			22/57 Niña base 39%	24/57 Niña base 42%	32/57 Cool base 56%	26/57 East base 46%	16/57 −IOD base 28%	16/57 −SOI base 28%	20/57 Weak base 35%	15/57 −PNA base 26%	22/57 −EPO base 39%	18/57 −WPO base 32%	16/57 −AO base 28%	11/57 −NAO base 19%

Mammoth Mountain (Main Lodge, ~8,900 ft): Resort-reported. Pre-October snow is counted in October. The measurement site has moved over the years. Source: www.mammothmountain.com. Seasons 1969-70 to 2025-26 — the driver record starts with 1950-51.

Driver values are 3-month (or Oct–Apr) means of RONI, PDO, QBO 50 hPa, DMI, SOI, the 10 hPa vortex and the CPC circulation indices, from the same archive as the Analog Builder. ENSO event peak is the strongest 3-month RONI of that ENSO year. “Now” readings are the latest published month or 3-month window, not a forecast for the coming season. Driver state alone doesn’t determine a season’s snowfall.