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Saturday, October 23, 2021 11:54 PM PDT

2020-2021 Rain Season Review and Totals

By Reginald Stanley. Posted July 1, 2021, 9:32 PM.



A moderate-strength La Nina pattern took hold over the equatorial Pacific Ocean during the winter of 2020-2021, with the result being widespread below-average rainfall across the entirety of the state of California. It was the first below-average rainy season in the region since 2017-2018.

Season totals ended below 10 inches at all active WeatherCurrents stations, with most locations receiving barely half of season averages. In Temecula, where precipitation records date back to 2000, the 2020-2021 rainy season ended as the third-driest rainy season there in at least 20 years. The number three spot was previously held by the 2017-2018 season in Temecula, with only 2001-2002 and 2006-2007 being drier. Many other WeatherCurrents stations also recorded lower season totals than in 2017-2018. In some other locations, including Murrieta, Perris, San Jacinto, 2017-2018 was drier still. WeatherCurrents' station in East Hemet recorded the highest season total with 9.11 inches - however, several of those inches are owed to a single very wet thunderstorm that hit the area in August 2020. The lowest season total was a mere 3.20 inches in Pinon Hills, a typically dry location made even drier this year. Other season totals included 8.67 inches in East Highland (courtesy of Peter Michas) as well as 5.92 inches in Temecula Valley's Wine Country (courtesy of Jim Sappington).

For a wider context, precipitation records in Downtown Los Angeles and San Diego - where they date back to 1877 and 1850, respectively - show 2020-2021 in the top ten driest rainy seasons in both locations. In Downtown Los Angeles, 2020-2021's total of 5.82 inches was the seventh driest season total since 1877. In San Diego, their season total of 4.51 inches was the tenth driest since 1850 - in over 170 years of continuous precipitation records.

The pattern of storm frequency, strength and rainfall distribution throughout the 2020-2021 winter was sporadic and generally uneven. The season had a slow, dry start with a weak cold front in early November 2020, after which a dry period took hold for an extended period of time. The only significant storm of the season that delivered widespread high rain amounts occurred in late December of 2020, which also brought relatively low snow levels to the region. After yet another extended dry period, a moderate atmospheric river event delivered some much-needed rain in late January of 2021, along with several additional events (including a number of local hailstorms) in early March. February 2021 was unusually very dry, with only light drizzle occurring in some locations around the middle of the month. One final late-season storm, albeit a weak one, delivered small amounts of rain in late April. Outside of these events, the 2020-2021 season was largely inactive.

The worsening drought conditions put the entire state of California in varying degrees of drought by Spring 2021, with over 50 percent of the state in severe or extreme drought, according to the Climate Prediction Center. As of June 2021, all of California, along with most of the Western United States, was experiencing drought conditions. As of July 1st 2021, the Climate Prediction Center has not yet released any ENSO-related warnings for the Summer or Fall of 2021. ENSO conditions are expected to remain neutral throughout the summer.

Here are the season totals for the WeatherCurrents network and associates. WeatherCurrents stations in Lake Elsinore, Wildomar, Riverside (Presidential Park), Anza, and Beaumont (Cherry Valley) were excluded due to large precipitation data gaps during the season. Season averages were only calculated for stations with more than 5 years of complete precipitation data:

Location 2020-2021 Season Average Source
East Hemet 9.11"  12.45"  WeatherCurrents
East Highland 8.67"  13.30"  Peter Michas
South Fallbrook 6.91"  14.64"  WeatherCurrents
De Luz 6.86"  15.22"  WeatherCurrents
French Valley 5.99"  10.38"  WeatherCurrents
Temecula Valley Wine Country 5.92"  15.06"  Jim Sappington
Northwest Murrieta 5.90"  13.11"  WeatherCurrents
Moreno Valley 5.84"  10.23"  WeatherCurrents
South Temecula 5.58"  12.66"  WeatherCurrents
Central Murrieta 5.40"  10.83"  Reginald Stanley
San Jacinto 5.24"  9.79"  WeatherCurrents
Perris 5.15"  9.08"  WeatherCurrents
Riverside (Orangecrest) 4.67"  N/A WeatherCurrents
Simi Valley 4.15"  10.13"  WeatherCurrents
Pinon Hills 3.20"  N/A WeatherCurrents
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