SLO County had driest January and February in more than 150 years — is this the ‘new normal’?

After reviewing 153 years of rainfall records from Cal Poly’s Irrigation Training & Research Center, there has never been a back-to-back dry January followed by a parched February in San Luis Obispo County.

Over the many decades of rain data, if you saw a primarily dry January, it would be followed by a wet February and vice versa during the peak of our rainy season (July 1 through June 30).

The pattern started to change about 55 years ago, when in 1967, a minuscule 0.58 of an inch of rain was recorded during the combined period of January and February. The January and February of 1984 saw just 1.15 inches, while in 2020, 0.46 of an inch was recorded.

This year, only 0.04 of an inch was reported, the driest combined January and February since 1871, when Cal Poly’s rainfall records started.

And not just Cal Poly, but the entire Central Coast has been nearly dry in 2022.

So far this year, the Santa Maria Airport has only recorded 0.24 of an inch of precious precipitation, while the Paso Robles Airport has seen 0.29 of an inch.

Up north, San Francisco’s last “significant” rain was 47 days ago, making this the fourth-longest winter “dry period” in its 173-year period of record.

Rather than using only days with zero rain days, Jan Null of Golden Gate Weather Services uses the minimal (i.e., < 0.08”) events like the one that occurred over last weekend (0.04”) or drizzle events that accumulate a few hundredths. If no rain falls through March 6, which seems likely, San Francisco will tie its longest wintertime dry period at 57 days, according to Null.

Dry rainy seasons becoming more common

Drier than typical rain season years may become the new normal.

A recent Tribune article trended the rainfall data from Cal Poly over the last 50 years: The average long-term amount of rain that falls appears to be trending downward.

In 2002, now retired climatologist Bill Patzert predicted a decades-long drought for California due to changes in the Pacific Decadal Oscillation (PDO) and global warming, which he now calls global heating.

The hypothesis Patzert made more than two decades ago for the Western United States has verified. He predicts that this condition will continue for much of California in the future.

That is not very reassuring since we live in a semi-arid area.

“We’ve really been in a drought since 2000, with some wet years (2005, 2010, 2011 and 2017) in Central California,” Patzert told me. “The wax and wane of wet years have given many a false sense of security.”

Patzert said California has entered a “new normal of significantly more dry years,” which results in “lower lake levels, less groundwater, depleted aquifers and skimpier Sierra Nevada snowpack.”

“The reemergence of this large-scale PDO pattern tells us there is much more than an isolated La Niña occurring in the Pacific Ocean,” he said. “This multi-year Pacific Decadal Oscillation ’cool’ trend can intensify La Niña or diminish El Niño impacts around the Pacific basin.”

Patzert’s observation on how the cool phase of the PDO produces below-average precipitation seems to be verified by the ongoing drought raging throughout the western United States.

The U.S. Bureau of Reclamation expects Lake Mead, the largest reservoir in the United States, to drop 34 feet from its current level of 1,067 feet above sea level to 1,033 feet by November of 2023.

That would be its lowest level since Franklin Delano Roosevelt was president.

PG&E expanding greenhouse gas-free electricity

To help combat climate change, PG&E customers received more renewable and greenhouse gas-free electricity in 2021 than ever before. PG&E’s mix of electricity sources remains among the cleanest in the nation.

Overall, 93% of its customers’; electricity came from greenhouse gas (GHG)-free resources, including renewables, nuclear and large hydroelectric power.

This story was originally published March 1, 2022 at 5:00 AM with the headline "SLO County had driest January and February in more than 150 years — is this the ‘new normal’?."