Parts of Fire-Weary California Suffer Through One of the Longest Waits For the Rainy Season on Record

Jonathan Erdman
Published: November 7, 2019

Parts of California may reach one of their driest starts to the rainy season on record with no rain in sight to quench the fire-weary state's thirst.

In recent weeks we've seen a number of destructive wildfires in California fanned by Santa Ana and Diablo winds, including the Kincade Fire in Sonoma County and the Tick, Saddleridge, Getty and Easy Fires in Southern California.

There have still been spot wildfires in recent days, long after those winds diminished, including the Jake Fire in northern Los Angeles County Wednesday that was quickly brought under control.

UCLA climate scientist Daniel Swain noted a measure of vegetation flammability is near or above record levels for early November.

Point is, the state remains a tinderbox.

It's the Rainy Season In Theory

California has distinct wet and dry seasons, unlike most areas of the country.

Over 90% of their annual average precipitation falls from October through April.

Rainfall typically returns to California by October as the jet stream begins to sag farther south, dragging Pacific frontal systems with it.

Average monthly rainfall in downtown Los Angeles, based on 1981-2010 data.
(Data: NOAA/NWS)

But that hasn't happened this fall.

No rain has fallen since October 1 in Sacramento, Fresno, Los Angeles or San Diego.

Downtown San Francisco's paltry 0.01 inch of rain since Oct. 1 is their driest start to the rainy season since 2013, over 1.6 inches below their average during that time. Only 12 other years dating to the mid 19th-century started out as dry or drier in as the current rainy season in San Francisco.

Why So Dry?

Blame the jet stream's position for the lack of rain so far.

A persistent dome of high pressure near the West Coast this fall deflected the jet stream well north of California.

As the jet stream goes, so goes the storm and all of its rain and mountain snow.

The general jet-stream pattern responsible for keeping California dry since October is a bulging ridge of high pressure aloft, deflecting the jet stream well north of California.

The jet stream enhanced Santa Ana and Diablo winds winds, rather than wringing out any rain or mountain snow, the only time it neared California in October.

The weather on a visible satellite image on Wednesday, with its lack of clouds anywhere over the Southwest

The weather in a visible satellite image over California Wednesday looked more like June than early November. A lack of clouds over the Southwest

The weather on a visible satellite image Wednesday shared by L.A. meteorologist Rick Dickert looked more like June than early November, with a lack of clouds over the Southwest, save for near the coast and some inland western valleys.

Any Relief Ahead?

The short answer here is probably not.

The majority of computer forecast models suggest the state should remain dry through at least the middle of next week. A few models suggest some light rain may make it into parts of Northern California late next week, but even if that occurs, it wouldn't be a soaker by any means.

NOAA's 8- to 14-day outlook suggests drier than average weather will continue to dominate the West Coast into the week before Thanksgiving.

This prolonged dry spell may push parts of the state toward its record latest first rain of the wet season.

In the San Joaquin Valley, it appears this year will be one of the five latest first rains.

The latest wait for the wet season to begin in downtown Los Angeles came in 1903-04, when measurable rain didn't first fall until January 18.

This doesn't necessarily mean this wet season, including Sierra snowpack crucial for the state's water supply, is in jeopardy going forward.

As the National Weather Service in Sacramento pointed out, last fall also started out dry, but ended up with plentiful precipitation in Northern California through spring.

A soaking rain isn't necessarily the best-case scenario to hope for either.

Even modest rain can produce destructive mud and debris flows over land recently charred by fires.

Despite that, we now have a scenario in which sun-loving Californians may actually be dreaming of rain.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.


The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.