The current year started off wet and cool for most of coastal Southern California (Jan-Mar), and it continued cool and very cloudy for most of the spring (Apr-Jun). Here in Westlake Village the winter rainfall amounts were as follows:
Nov 1.19″, Dec 5.47″, Jan 9.69″, Feb 7.61″, Mar 8.33″, Apr 0.04″, and May 0.70″
The July to June seasonal rain total was an impressive 33.25″, which is a little more than double the average here from 2000 to 2022 (15.41″).
Perhaps more impressive for the first six months of 2023 was the consistency of the cooler-than-normal maximum temperatures, and the almost total absence of warm-to-hot weather. The highest temperature at my Westlake Village/Northgate weather station (this is the official cooperative weather station for the National Weather Service in Westlake Village) for the first six months of 2023 was only 89F. That was reached on April 21. The first 90-degree day for 2023 did not occur until July 1 (91F). This is the first instance since I started daily observations in Westlake Village in 2000 that zero 90F maximums were counted from January through June. Closest was 2010, which reached only 91F (in May) during the first six months.
Here are the average max and min temperatures, and departures from the long-term 2000-2022 average, at Westlake Village for Jan-Jun 2023:
Jan 60.2/38.9 -6.1/-0.7
Feb 63.5/35.9 -3.4/-3.2
Mar 61.1/40.5 -9.3/-1.9
Apr 71.5/43.0 -1.7/-2.3
May 70.2/50.0 -6.9/-1.6
Jun 73.5/51.1 -9.0/-2.6
Departures of the maximum temperature of nearly ten degrees are quite uncommon in this region! Looking at each month individually:
The average maximum of 60.2F in January 2023 is the coldest since I began observations in Westlake Village in 2000. Next coldest is 60.6F in 2008. The monthly maximum of only 69F in Jan 2023 made it the only January to not reach at least 70F since 2000. All other Januarys beginning in 2000 reached at least 75F.
The average maximum of 63.5F in February 2023 was the 6th coolest in the last 24 years. The average minimum of 35.9F was the second coldest average minimum for Februarys since 2000.
The average maximum of only 61.1F in March 2023 is the coldest average maximum for any March on record (since 2000). Next coldest is 61.2F in 2006. All previous Marches since 2000 had at least one maximum of 79F or warmer, but March 2023 reached only 73F.
April 2023 was only a couple of degrees cooler than average, but its average maximum of 71.5F was the coolest since April 2010 (67.5F).
The average maximum of only 70.2F for May 2023 was the second lowest for all Mays in Westlake Village since 2000. (The average maximum in May 2019 was 70.1F.). The monthly maximum of 83F for May 2023 is the second lowest for all Mays since 2000.
The average maximum for June 2023 in Westlake Village was a paltry 73.5F, nine degrees below the average from 2000 to 2022! The 73.5F average maximum is by far the lowest of all Junes since 2000. Next coolest now is the 76.7F in June 2011. By comparison, a couple of Januarys and one December since 2000 had an average maximum warmer than that for June, 2023.
As you might expect, the cool conditions during the first six months of 2023 were due to persistent cool-to-cold troughs of low pressure along or near the California coast. This pattern was conducive to bringing moderate-to-strong onshore flow at low levels. With local ocean-water temperatures cooler than normal, the marine air influence was especially pronounced. Days with warm offshore flow were few from January to June. There were only 11 maximums of 70F or more from January to March, and 54 maximums of 70F or more from April to June. There were no days with 80F or more from January to March and only 12 days with 80F or higher from April through June.
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