SLO County has recorded 2 to 5 times its normal rainfall to date. Here are the totals
San Luis Obispo County has been absolutely drenched by the recent storms that have pummeled California, and data from the National Weather Service and county Public Works show exactly how abnormally rainy it has been.
Just in the month of January, the county had received anywhere from 3.75 inches of rainfall in the dry grasslands of the Carrizo Plain to more than 21 inches in the temperate mountains northeast of Cambria, as of Jan. 14.
That’s brought season totals to between 200% and 500% of normal for this point in the year, and it’s caused some catastrophic results.
Intense rainfall earlier this week tested the county’s infrastructure — eroding roads, turning dry creekbeds into rushing rivers, inundating homes and businesses, and overwhelming water retention and sewage facilities in some places.
How this year’s rain compares to an average year
The National Weather Service’s rain season for California runs from Oct. 1 through Sept. 30 every year. That’s because the rain typically starts to fall in October for most parts of the state.
The Weather Service’s rain year is different from the county’s, which runs from July 1 to June 30.
The two agencies also gather data from different locations, with the Weather Service tracking more remote spots and county Public Works more often monitoring cities.
Either way, however, San Luis Obispo County has already received far more rainfall to date than it normally would have as of Thursday.
For example, the dry Carrizo Plain has seen 244% of the rainfall it typically averages from Oct. 1 through Jan. 12, while Rocky Butte is at 527% to for that same period, according to the Weather Service’s data.
The pattern persists countywide, and everywhere seems to have received two to five times the total rain it usually gets for this time of year.
Even when you look at how much rain has fallen across the county to date compared to how much typically falls over the course of an entire rain year, many areas are already past their annual totals, with several months to go.
Rocky Butte is again the winner here.
It’s received 47.9 inches of rain from Oct. 1 to Jan. 12, when it normally measures 20.26 inches for the entire year ending Sept. 30, according to the Weather Service.
That means the spot has already recorded 236% of its total average annual rainfall, the Weather Service’s data show.
Cambria, Paso Robles and Santa Margarita also have already seen more rain so far than usually measured in an entire rain year, according to the Weather Service.
Data from the San Luis Obispo County Public Works Department somewhat mirrors that of the Weather Service.
Many major cities and communities in the county have already seen more rain so far this season — beginning on July 1 — than typically measured in a year.
Camp San Luis Obispo had measured 23 inches as of Jan. 12, 116% of its normal annual rainfall, according to the county. Los Osos (19 inches, 107%), Templeton (19 inches, 105%), Santa Margarita (25 inches, 104%) and Lopez Dam (25.3 inches, 126%) had also already measured more rainfall to date than their normal annual amounts, the county’s data show.
Falling just under were Oceano (14.5 inches, 91%), Atascadero (17.5, 97%) and Arroyo Grande (17.1 inches, 95%), according to the county’s data.
San Luis Obispo County usually sees rain continue to fall through March before the region dries out over the summer months.
That means those rainfall percentages will continue to rise — although by how much is yet to be seen.
What’s ahead in the forecast?
In the immediate future, the county expects to see another 1 to 2 inches or more of rain fall this weekend, according to the Weather Service’s latest forecast.
In a week or two, however, the weather pattern will likely shift into a dry spell.
That’s according to Daniel Swain, a climate scientist at UCLA, who is forecasting an end to the wet weather in the latter part of the month.
“And there is now a plausible end in sight,” Swain tweeted on Jan. 10. “Multi-model ensembles continue to suggest a return to a West Coast ridge pattern in about 9-10 days (by Jan. 20) — probably giving folks a much-needed chance to dry out and dig out”
Swain noted in a follow-up tweet that the break in the rain won’t come until about Friday, and it’s difficult to tell how long the dry spell will last.
This story was originally published January 14, 2023 at 5:30 AM.
