Downtown Los Angeles (USC) ended the 2020-21 rain year (July 1 to June 30) with 5.82 inches of rain. This is about 41% of the new normal annual precipitation total of 14.25 inches. Much of the West recorded below average precipitation for the rain year.

The amount of rainfall that is considered "normal" for Downtown Los Angeles has decreased nearly an inch in the past three decades. The normal rainfall for Los Angeles was 15.14 inches based on 1971-2000 climate data, and dropped to 14.93 inches based on data from1981-2010. Analysis of 1991-2020 data provided the new normal of 14.25 inches. Interim 2006-2020 climate data is shockingly dry, with normal rainfall in Los Angeles calculated at only 11.39 inches! For more info see U.S. Climate Normals and Normals Calculation Methodology 2020 (PDF).

La Nina conditions developed in August 2020 and transitioned to ENSO-neutral in April 2021. The Oceanic Nino Index (ONI) decreased to a minimum of -1.3 in the Oct-Nov-Dec season. The EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION issued August 12, 2021 projects a 70% chance of La Nina conditions being present during November-January.

Los Angeles rainfall during La Ninas has been variable, but skewed to the drier side. The average rain year precipitation for the 24 ERSST.v5 ONI-based Cold Episodes since 1949 is 11.84 inches. The highest amount was 20.20 inches in 2010-11 and the lowest 4.68 inches in 2017-18. In the past decade, rainfall totals for Los Angeles have been less in the second year of successive cold episodes, but this pattern doesn't hold up over the entire record.

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

Downtown Los Angeles (USC) ended the 2018-19 rain year (July 1 to June 30) with 18.82 inches of rain. This is about 126% of the normal yearly precipitation total of 14.93 inches. Much of the southwest recorded average to above average precipitation, thanks to a generally progressive pattern in the West and a strong Pacific jet this Winter.

Based on the CPC's Oceanic Nino Index (ONI), equatorial Pacific SSTs capable of supporting El Nino conditions developed in the Sep-Oct-Nov 2108 season, but ocean-atmosphere coupling characteristic of El Nino did not develop until January 2019.

Although this year's El Nino was weak and somewhat atypical, it should be noted that the Global Wind Oscillation orbited through positive AAM phases from mid October until just recently. Historically, continually positive AAM anomaly values during the Nov-Mar period have occurred during strong El Ninos, such as in 1997-98 and 1982-83. The Nov-Dec GWO Phase Plots for ONI-based warm episodes can be found on our El Nino Comparison Chart for 2018-2019 page.

There is some evidence that suggests Southern California precipitation is more closely correlated with AAM than with Nino 3.4 SST.

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

The graphic above is color-coded chart of Los Angeles (KCQT) rain year precipitation from 1877 to 2017, a period of 141 years. Years progress from left to right. The rain year is from July 1 of the indicated year to June 30 of the following year. Colors are indicative of the following amounts of rain:

Red: VERY DRY - less than 5 inches of rain.
Orange: DRY - more than 5 inches of rain, but less than 13 inches.
Light blue: ABOUT AVERAGE - more than 13 inches of rain, but less than 17 inches.
Blue: WET - more than 17 inches of rain, but less than 22 inches.
Dark Blue: VERY WET - more than 22 inches of rain.

Following are some observations regarding Los Angeles rainfall:

- VERY DRY and DRY years (orange & red) have been more common than VERY WET and WET years (blue & dark blue). In the first 70 years there were a few more dry years than wet years (30 vs. 25). In the last 70 years there have been about twice as many dry years as wet years (41 vs 20).

- Extended dry periods (orange & red) have been more common than extended wet periods (blue & dark blue) and generally last longer. The longest uninterrupted dry period is 7 years, while the longest wet period is only 3 years. If we allow for one interceding year, the longest dry period is 11 years and the longest wet period is 5 years.

- There were no VERY DRY years (red) prior to 1960 and three of the four VERY DRY years have occurred since 2001.

- ABOUT AVERAGE years (light blue) have not been common. Only 24 of 141 years (17%) have had ABOUT AVERAGE rainfall. The first 70 years had 15 ABOUT AVERAGE years and the last 70 years had 9 ABOUT AVERAGE years.

- Overall, VERY WET years (dark blue) have been more common than VERY DRY years (red), but in the last 30 years the number of VERY WET years (4) and VERY DRY years (3) have been about equal.

- Consecutive VERY WET (dark blue) or VERY DRY years (red) have been rare. There has been one instance of back-to-back VERY WET years (1956 & 1957) and no instances of back-to-back VERY DRY years.

Here is a PDF of the rainfall chart. The chart includes the January - December precipitation amounts for each year, as well as the rain year value.

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

Downtown Los Angeles (USC) has ended the 2017-18 rain year (July 1 to June 30) with only 4.79 inches of rain. That makes 2017-18 the third driest rain year since recordkeeping began in July 1877. The rainfall total was only 32% of normal and is less rain than was recorded during any rain year in our recent five year drought. The three driest rain years in Los Angeles have all occurred since 2001.

The June 2018 EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION says El Nino conditions are favored to develop during the Northern Hemisphere fall, and and this is the most likely ENSO state to be present this winter. According to the CPC/IRI consensus forecast there is a 50% chance of El Nino conditions developing this fall, with the probability increasing to about 65% this winter.

Keeping in mind last year's "failed" El Nino, the April-May value of the Multivariate ENSO Index (MEI) increased 0.9 SD to 0.47. This is just below the threshold of a weak El Niño ranking. Klaus Wolter's empirical analysis using historical analogues suggests that, compared to last month, the odds for the development of El Niño conditions later this year have dramatically increased.

If Los Angeles rain year precipitation is averaged for El Nino episodes (CPC ERSSTv5) since 1950, the average is about 120% of normal. However, El Nino conditions do not guarantee above average rainfall, particularly in the last 15 years or so. The driest rain year on record in Los Angeles (2006-07) was during an El Nino; and two rain years (2014-15 & 2015-16) of our recent five year drought were during an El Nino.

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

Downtown Los Angeles (USC) finished the 2016-17 rainfall year (July 1 to June 30) with 19.00 inches of recorded precipitation. This is about 127% of the 1981-2010 normal of 14.93 inches. This was the first rain year with above normal precipitation at Los Angeles since 2009-2010, when 20.2 inches was recorded.

As of May 2017 the Pacific Decadal Oscillation Index has been positive (warm) since January 2014 -- a record 41 consecutive months. The previous record streak was 36 months, from August 1991 to July 1994.

Most climate outlooks are projecting ENSO Neutral conditions are favored to persist into the Northern Hemisphere fall, with a lesser chance of weak El Nino conditions developing over that period. Perhaps supporting the notion of El Nino development, the April-May value of the Multivariate ENSO Index (MEI) increased by 0.69 standard deviations from 0.77 to 1.46. This is solidly within the index's El Nino ranking and at the threshold of a strong El Niño ranking. According to Klaus Wolter, the increase over the last three months is the second largest on record for this time of year, exceeded only by 1997. We'll see if ENSO conditions remain neutral or some form of ENSO warming (Central Pacific?) takes place.

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

Downtown Los Angeles (USC) finished the 2015-16 rainfall year (July 1 to June 30) with 9.65 inches of recorded precipitation. This is about 65% of the 1981-2010 normal of 14.93 inches. This was the fifth consecutive year of below normal rainfall for Downtown Los Angeles, with a cumulative rainfall deficit of 35.86 inches --nearly three feet!

Observable impacts of the drought are widespread. Trees have been particularly hard hit. Dead trees can be seen along city streets, in parks, and throughout the open space areas and wildlands of Southern California. The dead and dying 100+ year old coast redwoods at Malibu Creek State Park are an example.

Most climate outlooks are forecasting La Nina conditions to develop over the Northern Hemisphere summer. Historically La Ninas have "on average" resulted in below normal precipitation in Southern California. But historical composites can be misleading. During the last five La Nina episodes (1999-00, 2000-01, 2007-08, 2010-11, 2011-12) Downtown Los Angeles (USC) has averaged 14.39 inches of rain, which is 96% of normal.

Even during one of three strongest El Ninos on record, precipitation outlooks based on historical composites and analogs didn't perform well in Southern California. Given the somewhat more variable rainfall in Southern California during La Ninas, to determine the winter precipitation outlook you might as well flip a three-sided coin.

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

Downtown Los Angeles (USC) ended the 2014-2015 rainfall year (July 1 - June 30) with 8.52 inches of rain; well below the normal of 14.93 inches. It was the fourth consecutive year of below normal rainfall in Los Angeles and much of Southern California.

To kick off the new new rainfall year two waves of moisture and instability associated with ex-hurricane Dolores, other tropical sources, and a strong monsoonal flow from Baja resulted in record-setting rainfall in Southern California from Saturday July 18 to Monday July 20.

Constructive interference of the El Nino base state by the active phase of the MJO resulted in negative 200-hPa velocity potential anomalies and enhanced convection in the Eastern Pacific during the first half of July. This appears to have contributed to the rapid development of Dolores from a tropical depression on July 11 into a Category 4 hurricane July 15. Anomalously warm SSTs in the tropical and sub-tropical Eastern Pacific also played a role, helping to maintain the strength of Dolores and increasing the amount of water vapor entrained by the system and transported into Southern California.

Many stations set new records, not only for the date, but for any day in July. Downtown Los Angeles (USC) set rainfall records for the date on Saturday and Sunday and tied Monday's record. Downtown Los Angeles recorded 0.36 inch of rain Saturday. This is more rain than any day in any July since recordkeeping began in 1877. That one day of rainfall even broke the monthly record for July in Los Angeles! Prior to this event the wettest July on record was in 1886, when 0.24 inch was recorded.

There was very heavy rain in the mountains on Sunday, with rain rates exceeding an inch a hour. From 5:15 p.m. to 5:25 p.m. a CBS Radio weather station on Mt. Wilson recorded a half-inch of rain in just 10 minutes!

Though the rain created its own problems -- including flash floods, debris flows and rock slides -- the soaking rains helped quell the Pines Fire near Wrightwood and the North Fire near Cajon Pass. Over the three day period from Saturday to Monday the Big Pines Remote Automated Weather Station (RAWS), near the Pines Fire, recorded 3.12 inches of rain. Several stations in the San Gabriels recorded more than three inches of rain, including Clear Creek and Opids Camp. Here's a NWS compilation of some rainfall totals in the Los Angeles forecast area and the San Diego forecast area.

After dawdling around for several months our on again, off again El Nino is finally firing on all cyclinders and could reach ONI and MEI levels not seen since 1997-98 and 1982-83. The Multivariate ENSO Index (MEI) for May-June was 2.06. This was the third highest value for the season, exceeded only in 1983 (2.2) and 1997 (2.3). It is the second highest for the season during the development phase of an El Nino event. The 2015 April-May-June Oceanic Nino Index (ONI) value of 0.9 was higher than than in 1982 (0.6) and 1997 (0.6). Several dynamical models in the IRI/CPC ENSO Predictions Plume of forecast Nino 3.4 SST anomaly, released July 16, project Nino 3.4 SST anomalies in excess of 2.5°C this fall.

Analysis of correlations of CMAP Precipitation with globally integrated atmospheric angular momentum using ESRL/PSD's Linear Correlations in Atmospheric Seasonal/Monthly Averages tool suggests that precipitation in the southern half of California is more strongly correlated with atmospheric angular momentum (AAM) than with Nino 3.4 SST. For example, compare the correlation of CMAP Precipitation to AAM and to Nino 3.4 SST for Dec-Jan-Feb 1980-2012. Cyclical increases in relative atmospheric angular momentum are often associated with El Ninos. This can be seen in the plots of the Global Wind Oscillation in my El Nino Comparison Chart.

After being negative for 3 1/2 years, the PDO Index has been positive since January 2014. December's PDO value of 2.51 was the highest for that month on record since 1900. June's value of 1.54 was the 13th highest since 1900.

More information about Southern California weather and climate can be found using our WEATHER LINKS page.