Cold fog and palms!

[Josue Diaz]

The last month of endless "Tule Fog" (radiation fog) in California's central valley has done some damage to marginal plants, despite temps not dropping below 40F except for two instances when we dropped to 39F. From November 21st, for more than 3 weeks, we did not see the sun, and temps did not exceed 50F. We were stuck in an endless cycle of lows in the low 40s, and highs in the high 40s, paired with 90% humidity. Everything wet, everything cold, no wind. Just stagnant, cold, wet air. 365+ consecutive hours of it. I think we broke a record this year for the most consecutive hours in the 40s Fahrenheit AND the longest fog event in recorded history for this area.

While most of the state had clear skies and warm weather, we were under this 400-mile long stretch of cold fog. 

My plumerias are wrecked, I'm seeing dead tissue and rot at the tips. Most palms seem ok. 

Here are some winners and losers from that type of cold spell - frost free but cold and wet. 

Chrysalidocarpus mananjarensis - second winter. Seems to be ok with prolonged cold and wet.

Chrysalidocarpus "Blue Decipiens" (which i understand is one of the "ugly Betafaka) has no issues with it either.

Chrysalidocarpus ambositrae looking great as always

Syagrus sancona - really thought this would be ok with extended cold and wet since they're grown extensively at high elevation in Colombia... 

Gaussia gomez-pompae seems ok with it. Tiny bit of spotting.

Brahea pimo spotting pretty extensively 

The big loser, roystonea regia. Despite being well within this species' temp range, the prolonged "refrigerator-like" conditions really wrecked it. Sunnier and drier conditions are coming back so hopefully this pulls through. Might bring it indoors. 

Lastly, a shot from my friend's front yard just ABOVE the fog at around 1700 feet above sea level. 70s and sunny there, and just 3 miles downhill, 40s and visibility less than 30 feet. 

If anyone wants to read more about the phenomenon, here's a good link: https://weatherwest.com/archives/43605

 

Anyone else in the valley seeing similar damage? 

[kinzyjr]

8 minutes ago, Josue Diaz said:

If anyone wants to read more about the phenomenon, here's a good link: https://weatherwest.com/archives/43605

Now that is some freak weather there!

[Silas_Sancona]

6 hours ago, kinzyjr said:

Now that is some freak weather there!

Definitely some of the wildest weather …over pretty short distances… someone can experience anywhere in the US .. if not further out in scope.

Grew up knowing this pattern pretty well and experienced it first hand again while out there at the start of the month .. and was still pretty surprised by just how localized and extreme the effect is.. 

Wild is thinking about how hot it can get in these same areas come July and Aug.  .. about as hot as we can get here at times just with a touch more humidity than we have  - outside of raised humidity on stormy monsoon days. 

For perspective:

Normally cool -ish ( this time of year ) 60s in San Jose,  once any patchy morning marine layer / spill over from the valley cleared off while there  felt fairly warm,  compared to darn near freezing at 39\40 -something degs.  In dreary, damp dense fog,  in a hoodie /  beanie that did nothing to block that type of chill while passing thru the central valley on the way to/ back from San Jose. 

Whole time i was  driving “ in the fog “ out there,  was thinking to myself “ this prolonged, day after day, cool / clammy, damp, and cloudy pattern cant be good for x y and z tropical - ish stuff in people’s gardens“. 
 

@Josue Diaz if you can,  …and any damage you're seeing is currently confined to just the tips of effected specimens,  get the plumeria under cover / covered,  and get out the sulfur dust.  
 

hopefully any damage isn’ t serious / progresses to that stage before the wx pattern heads in a better direction for them. 

[Josue Diaz]

9 hours ago, kinzyjr said:

Now that is some freak weather there!

Made me green with envy that I could drive 30 mins uphill and find plenty of warmth and sunshine lol

1 hour ago, Silas_Sancona said:

Definitely some of the wildest weather …over pretty short distances… someone can experience anywhere in the US .. if not further out in scope.

Grew up knowing this pattern pretty well and experienced it first hand again while out there at the start of the month .. and was still pretty surprised by just how localized and extreme the effect is.. 

Wild is thinking about how hot it can get in these same areas come July and Aug.  .. about as hot as we can get here at times just with a touch more humidity than we have  - outside of raised humidity on stormy monsoon days. 

For perspective:

Normally cool -ish ( this time of year ) 60s in San Jose,  once any patchy morning marine layer / spill over from the valley cleared off while there  felt fairly warm,  compared to darn near freezing at 39\40 -something degs.  In dreary, damp dense fog,  in a hoodie /  beanie that did nothing to block that type of chill while passing thru the central valley on the way to/ back from San Jose. 

Whole time i was  driving “ in the fog “ out there,  was thinking to myself “ this prolonged, day after day, cool / clammy, damp, and cloudy pattern cant be good for x y and z tropical - ish stuff in people’s gardens“. 
 

@Josue Diaz if you can,  …and any damage you're seeing is currently confined to just the tips of effected specimens,  get the plumeria under cover / covered,  and get out the sulfur dust.  
 

hopefully any damage isn’ t serious / progresses to that stage before the wx pattern heads in a better direction for them. 

Yeah! That damp cold just penetrates any sweatshirt or jacket. Most plants can tolerate these conditions for a short while, but the longer these conditions persist, the more cell death you start seeing on the more tropical stuff. Even completely "hardy" stuff begins to show signs of cell death - i have several mushy spots on some agave leaves. Agave attenuata boutin blue is especially sensitive. Agave marmorata and Agave celsii as well. Both hardy enough (i mean 39F is hardly a threat to these!) but they just begin to suffer in prolonged cold and wet. I also lost a nice astrophytum asterias. The substrate was bone dry, but the plant just melted. Too cold and too wet for too long. I found it oozing one morning and the entire plant was one mushy mess inside. 

The plumerias are south facing, so now that the fog is broken up by sunny afternoons, they are getting the sunlight they need, and also drying up. The last time I had damage similar to this was in 2022 with the long, cool, wet spring we had. I did remove all of the leaves to increase airflow and allow sunlight to penetrate. I also sprayed liquid copper fungicide on the stems, and applied a soil drench of Garden Phos as a systemic to guard against root and stem rot. I had anticipated a wet winter, so I had given them a dose of systemic in October, and again in November. This is the third application of the systemic,  so I'm hopeful that is enough to get them through. Fingers crossed for more sunshine! No more endless fog, please!

[Than]

Wow, that sounds worse than my 8 years in Scotland and England! I guess you have issues with fungi every winter?

Btw I noticed you plant Chrysalidocarpus-es in the ground quite early! 

My Roystonea wanted to say hi and send wishes for a speedy recovery to yours:

 

[Josue Diaz]

1 hour ago, Than said:

Wow, that sounds worse than my 8 years in Scotland and England! I guess you have issues with fungi every winter?

Btw I noticed you plant Chrysalidocarpus-es in the ground quite early! 

My Roystonea wanted to say hi and send wishes for a speedy recovery to yours:

 

Hah! Yeah I do have issues with some plants every winter. We do get this type of fog event regularly in winter, but it's not usually for this long. Many times, it'll last a few days, and more often it'll burn off by noon and we get breaks. Plumerias don't usually have problems with it. This fog spell was pretty long, even for us. More recently, because of extended drought, we've gone the entire winter without fog. It's such a short lived phenomenon (in 3 months we'll be hitting close to 100F) but it defines winter here

[SCVpalmenthusiast]

I thought only coastal areas experienced fog in California. How does this fog occur? I thought central valley was bone dry. 

[Josue Diaz]

9 minutes ago, SCVpalmenthusiast said:

I thought only coastal areas experienced fog in California. How does this fog occur? I thought central valley was bone dry. 

Nooooo the Central Valley is fog central from November through January, give or take. It doesnt always happen, but it can happen during these months when conditions are right. It usually begins with one of the rainstorms off the Pacific which soaks the soil. High pressure systems often form over the area which block new storm systems from blowing the cold, moist air out. Being that the valley is surrounded by a 14000 foot ridge to the east (the sierra nevada), and the coastal mountains on the west, the air has nowhere to go and condenses at ground level. As the air warms at higher elevations, the cold air sinks and compounds these conditions. The longer the fog lingers, the more dense it becomes. It often stays with us a day or two before the next storm moves in and clears the skies. This fog spell lasted approximately a month, which is pretty long even for us. 

[Josue Diaz]

Another big looser: Syagrus kellyana. Gets spotting every year but this year's fog really did a bit to it. Should grow out of it i think. 

Howea belmoreana, foresteriana, chamaedorea and chambeyronia were all made for this

 

Ficus dammaropsis seems happy in this also

[Patrick]

1 hour ago, Josue Diaz said:

Nooooo the Central Valley is fog central from November through January, give or take. It doesnt always happen, but it can happen during these months when conditions are right. It usually begins with one of the rainstorms off the Pacific which soaks the soil. High pressure systems often form over the area which block new storm systems from blowing the cold, moist air out. Being that the valley is surrounded by a 14000 foot ridge to the east (the sierra nevada), and the coastal mountains on the west, the air has nowhere to go and condenses at ground level. As the air warms at higher elevations, the cold air sinks and compounds these conditions. The longer the fog lingers, the more dense it becomes. It often stays with us a day or two before the next storm moves in and clears the skies. This fog spell lasted approximately a month, which is pretty long even for us. 

The way I'm seeing it/ looking at it: we've had these past several years of great weather in the winter here in the valley. THIS currently is normal winter weather- what I remember it to be. I think my little quote with my avatar here says 'cold wet winters'. I wrote that back in 2008 or so. This IS much more/ longer of a fog spell than memory serves, and it's foggy again today after a beautiful day yesterday.

 

Hopefully come January (super bowl time) we have sunny days again. I always seem to get much work done in the yard those (American) football weekends. We get lucky quite often each year and have pretty good weather those weekends if you don't mind 50s and low 60s with sun. I can tell how the game is going based on what part of the neighborhood is cheering. Bread and circuses.

 

My 100+ ambositrae seedlings have been chilling outside on the driveway, unprotected, in their community tub this whole time and look just fine. They haven't grown any (of course) but they haven't taken any damage. Everything else is looking decent given the conditions, but I have a pretty conservative yard after experiencing the 07 freeze. 

[Josue Diaz]

5 minutes ago, Patrick said:

The way I'm seeing it/ looking at it: we've had these past several years of great weather in the winter here in the valley. THIS currently is normal winter weather- what I remember it to be. I think my little quote with my avatar here says 'cold wet winters'. I wrote that back in 2008 or so. This IS much more/ longer of a fog spell than memory serves, and it's foggy again today after a beautiful day yesterday.

 

Hopefully come January (super bowl time) we have sunny days again. I always seem to get much work done in the yard those (American) football weekends. We get lucky quite often each year and have pretty good weather those weekends if you don't mind 50s and low 60s with sun. I can tell how the game is going based on what part of the neighborhood is cheering. Bread and circuses.

 

My 100+ ambositrae seedlings have been chilling outside on the driveway, unprotected, in their community tub this whole time and look just fine. They haven't grown any (of course) but they haven't taken any damage. Everything else is looking decent given the conditions, but I have a pretty conservative yard after experiencing the 07 freeze. 

Yeah I remember growing up with lots of foggy days. Though being a kid, you don't really pay attention to weather much. I was just getting into plants in 07, and graduating high school but I do remember it being a cold year. We've been trending towards drier winters, which tend to be sunny and fog free,  particularly in the southern end of the valley, and the Eastern side which is slightly elevated. Fog will tend to accumulate in the lower, western side (sunset zone 8), and spills into the delta.

I don't mind the rain, even an occasional fog spell. I just hope we don't have another extended fog spell like that for a long time. 

 

Ambositrae seems like it would do great in your area! 

[Jim in Los Altos]

As you can see in your aerial photo, some of that tule fog would spill into the Bay Area through the Delta but thankfully where I am, it would mostly  “burn off” in the afternoon leaving very hazy but sunny skies. The kind of chilly foggy weather in the Central Valley recently would have driven me berserk! So glad for you guys that it’s been blown out by Pacific storms. More rain on its way for several days starting Wednesday. 
 

[Silas_Sancona]

21 hours ago, Josue Diaz said:

Made me green with envy that I could drive 30 mins uphill and find plenty of warmth and sunshine lol

Yeah! That damp cold just penetrates any sweatshirt or jacket. Most plants can tolerate these conditions for a short while, but the longer these conditions persist, the more cell death you start seeing on the more tropical stuff. Even completely "hardy" stuff begins to show signs of cell death - i have several mushy spots on some agave leaves. Agave attenuata boutin blue is especially sensitive. Agave marmorata and Agave celsii as well. Both hardy enough (i mean 39F is hardly a threat to these!) but they just begin to suffer in prolonged cold and wet. I also lost a nice astrophytum asterias. The substrate was bone dry, but the plant just melted. Too cold and too wet for too long. I found it oozing one morning and the entire plant was one mushy mess inside. 

The plumerias are south facing, so now that the fog is broken up by sunny afternoons, they are getting the sunlight they need, and also drying up. The last time I had damage similar to this was in 2022 with the long, cool, wet spring we had. I did remove all of the leaves to increase airflow and allow sunlight to penetrate. I also sprayed liquid copper fungicide on the stems, and applied a soil drench of Garden Phos as a systemic to guard against root and stem rot. I had anticipated a wet winter, so I had given them a dose of systemic in October, and again in November. This is the third application of the systemic,  so I'm hopeful that is enough to get them through. Fingers crossed for more sunshine! No more endless fog, please!

In the  ..maybe.. 20 min I spent taking some pictures of the landscaping at the rest stop we'd  stopped at closest to 152, before heading over it,  I was frozen.

Honestly felt colder than most of the  37f evenings / mornings experienced while living in either KS or Ohio. Heck, lol can count many times one could find me removing snow from the parking spaces in front of the apartment building my mom lived in ( while in Ohio )  in shorts, a t shirt, and sandles.. 

 

Yeah,  imagine even the otherwise " hardy to lower 40s / highest 30s" stuff might start suffering under those conditions. 

Bummer regarding the Astro.

Sounds like it may have caught some sort of bacterial rot.  Had that occur w/ a few things here I'd kept too wet ( even though they were in pure grit and looked perfectly dry ) and in all day shade this time of year a few times. 

 

Speaking of the Plumeria.. No clue what caused it but caught one of the potted specimens out front ( JJ Ken's White ) w/ rapidly advancing tip rot today. 

Totally fine about a week ago and we've been dry and warm all month ..so I can't pin the damage on any cold  exposure..

Rest of the plants out there, inc the seedlings,  = perfectly fine.. 

 🤷‍♂️ plants sometimes.

..and yes.. think a month(+) of days under those skies is more than enough for anyone.  Honestly drove as fast as I could to get out of it. 

 

[Darold Petty]

Chrysalidocarpus ambositrae grows really well without heat, even for me !   

[Harry’s Palms]

Fog is what drove me away from the coast . We lived on a sailboat in Channel Islands Harbor for over 12 years and summers were brutal. It would be in the 60’s at the harbor and 5-10 miles inland , sunny and warm . Too far inland and it gets hot , we chose Santa Paula because it is warm but not too hot . Plus , when we bought out here , it was less expensive than Ventura . The fog follows the river but burns off mid morning . In this home we are above it most of the time. Altitude , even a few hundred feet , has its benefits . Harry

[Josue Diaz]

On 12/29/2025 at 1:29 PM, Josue Diaz said:

 

 

I sent this Roystonea to a new home in Riverside today. A friend there will give it a better life than I could. 

On 12/30/2025 at 1:01 PM, Jim in Los Altos said:

As you can see in your aerial photo, some of that tule fog would spill into the Bay Area through the Delta but thankfully where I am, it would mostly  “burn off” in the afternoon leaving very hazy but sunny skies. The kind of chilly foggy weather in the Central Valley recently would have driven me berserk! So glad for you guys that it’s been blown out by Pacific storms. More rain on its way for several days starting Wednesday. 
 

Yes! I was watching the forecast with a sort of obsession, waiting for when those storms might blow through. 

18 hours ago, Silas_Sancona said:

In the  ..maybe.. 20 min I spent taking some pictures of the landscaping at the rest stop we'd  stopped at closest to 152, before heading over it,  I was frozen.

Honestly felt colder than most of the  37f evenings / mornings experienced while living in either KS or Ohio. Heck, lol can count many times one could find me removing snow from the parking spaces in front of the apartment building my mom lived in ( while in Ohio )  in shorts, a t shirt, and sandles.. 

 

Yeah,  imagine even the otherwise " hardy to lower 40s / highest 30s" stuff might start suffering under those conditions. 

Bummer regarding the Astro.

Sounds like it may have caught some sort of bacterial rot.  Had that occur w/ a few things here I'd kept too wet ( even though they were in pure grit and looked perfectly dry ) and in all day shade this time of year a few times. 

 

Speaking of the Plumeria.. No clue what caused it but caught one of the potted specimens out front ( JJ Ken's White ) w/ rapidly advancing tip rot today. 

Totally fine about a week ago and we've been dry and warm all month ..so I can't pin the damage on any cold  exposure..

Rest of the plants out there, inc the seedlings,  = perfectly fine.. 

 🤷‍♂️ plants sometimes.

..and yes.. think a month(+) of days under those skies is more than enough for anyone.  Honestly drove as fast as I could to get out of it. 

 

I notice some cultivars are less hardy than others - within a few degrees of course. But some begin to show damage very early on and others can handle the cold better (i.e. less or no rot, slower to take on leaf damage, etc.) 

10 hours ago, Darold Petty said:

Chrysalidocarpus ambositrae grows really well without heat, even for me !   

Mine is one that I got from you several years ago! I think you had it in a 1g pot back then. 

8 hours ago, Harry’s Palms said:

Fog is what drove me away from the coast . We lived on a sailboat in Channel Islands Harbor for over 12 years and summers were brutal. It would be in the 60’s at the harbor and 5-10 miles inland , sunny and warm . Too far inland and it gets hot , we chose Santa Paula because it is warm but not too hot . Plus , when we bought out here , it was less expensive than Ventura . The fog follows the river but burns off mid morning . In this home we are above it most of the time. Altitude , even a few hundred feet , has its benefits . Harry

Santa Paula is beautiful. The avocado orchards surrounded by dramatic mountains are so spectacular to look at. 

[kylecawazafla]

Hoping for the best for your palms! 

[Harry’s Palms]

Your garden is lovely . I have seen your other posts . Hard to believe anything there is struggling , they all look happy. Harry

[Tracy]

On 12/29/2025 at 1:29 PM, Josue Diaz said:

The last month of endless "Tule Fog" (radiation fog) in California's central valley has done some damage to marginal plants,

 

On 12/30/2025 at 7:02 AM, SCVpalmenthusiast said:

I thought only coastal areas experienced fog in California. How does this fog occur? I thought central valley was bone dry. 

I never lived in the Central Valley, but traveled it a great deal over the decades.  Growing up in California public elementary schools both in the Bay Area and LA County, we learned about the Tule fog in school.  As I recall, water diversions, landuse changes with the advent of large scale agriculture and groundwater pumping changed the ecosystem from what it was and the prevalance of the Tule fog relative to say 100 plus years ago.  I will have to take a look at the link you provided Josue.  

When you mentioned Pacific storms playing a factor, I have to wonder if the flooding that recreated Lake Tulare a couple of years back triggered any of the changes.  

[Silas_Sancona]

On 12/31/2025 at 4:25 PM, Josue Diaz said:

I notice some cultivars are less hardy than others - within a few degrees of course. But some begin to show damage very early on and others can handle the cold better (i.e. less or no rot, slower to take on leaf damage, etc.) 

Yep..  You'll remember how i'd lost the ...30 - something... varieties i'd brought here when we left FL.  ..Not from any " cold " i've seen, but our crazy heat / sun exposure in the summer. 

That PDF i'd stumbled upon awhile back unlocked the " why did these croak " questions i had afterwards,  and has been helping w/ choosing varieties that ..so far at least.. are holding up well here.