Weather tracker: why is it so cold in California at the moment?

Throughout the past several months there has been a recurring theme in weather news about how wet and unsettled western parts of the US have been, particularly for the normally sunny state of California. This has been due to frequent atmospheric rivers funnelling into western North America, and a recent analysis undertaken by the Scripps Institution of Oceanography found that over the course of this water year (1 October 2022 to 30 September 2023), a total of 31 atmospheric river events have affected the west coast of the USA so far.

This constant barrage of precipitation to the western US has meant that March in particular has seen precipitation anomalies far above normal, with widely at least two to three times more than usual. In addition, it has been exceptionally cold, with average temperatures for March widely at least 2-3C below normal, but with many places also having seen temperatures more than 5C below normal. Because of this, mountainous regions have seen precipitation falling mostly as snow throughout the month, this very heavy and frequent and has brought snow accumulations enough to bury an entire ski lodge in Rimforest, California. Mammoth Mountain ski resort has declared this the snowiest season on record with snow totals reaching 17.6m at their main lodge and a staggering 22.1m at the summit of the mountain peak. Cold and wet conditions are still expected to linger at least through the next week.

Meanwhile Spain has been well and truly shaking off the spring feeling with many weather stations across Spain reaching above 30C on 29 March. The heat continued into the next day with temperatures in Murcia reaching 32.7C, very close to the March record for Murcia of 33.3C. March overall has been a widely warmer than average with temperatures at least 1-2C above normal for most areas. The heat had built from the south where northern Africa has been baking. Agadir in Morocco saw temperatures reach 39.8C on 29 March, beating the previous March record of 39.0C in 2005. This heatwave will subside through the weekend with temperatures returning a little closer to normal, but still above average.