I think that in the right microclimate it would probably survive since it seems to get warm enough for them in Avalon. They would need a nice wall and to be decently far inland so they aren't getting beat up by sea breezes during cooler times of the year.
I doubt they would do well there, but I know I'd be giving them a try if I had a yard there!
-Alex

Which Channel Islands are you talking about? The ones in the English Channel, or somewhere else? Where ever you are, much depends on how long you want them outside/unprotected.

The California Channels. Avalon would be a great chance. This winter,when Newport Beach was having a few hi 30's..If my memory is close, Avalon and the islands off of San Diego were not going much below 50f. z11 winter lows.

I've thought about this before. But I dont think many have tried it. I'm thinking its possible but they wont be easy. Just easier than SoCal on the coast. But another spot I've been wondering about is micro-climates in Imperial Valley and such. Some of that area is z10 and in the right micro-climate it may not ever really freeze.

- US_Marine

the primary limitation to growing coconuts is primarily heat, not just cold. I would be very surprised if a coconut could survive living on Catalina, but even less so on the Channel Islands... stays pretty cool on both those islands, though Catalina does get somewhat hot sometimes. I am pretty sure any coconut would eventual wither and die due to lack of heat unless planted right against a building with some light-absorbing coloration/matieral facing southwest... THEN it might eke along for a few years.

Coconuts have done fairly well inland in the southern deserts, though they still sometimes croak for some reason or other (possibly there it is the occasional cold following by insufficient warmth). Coconuts are frequently successfully grown in Central Florida where frosts and even freezes are common...just not severe enough to actually kill the palm... but these frosts/freezes are following immediately by heat and that is what saves them. Sans heat, they could not survive.

Hi
Always interesting when you visit a country within the tropics how lush and beautiful the Coconuts are and how quickly they disappear as you go up into the mountains
Obviously the only difference is temps since the only thing that changes is the average temps
Another side note as to the general appearance as compared to those in s. florida bigger,greener,lusher in every respect. Again the only obvious difference is winter?? gary

I looked at Avalons historical ave's. Basically its summers of 63f lows and 75f highs and in winter 50f low and 65f highs. If the fog is low in winter along with rainfalls...that's a lot of sunny days in winter.
Over the full year,70f and 56f..is that enough?

averages mean nothing to coconut palms... it is how often it is hot, and how hot it is, as well as what the cold minimums are. Many areas in California have higher historical averages to some areas of Florida where the cold dips skew their averages lower, but the highs are more frequent as well... allowing coconuts to survive while in California, for the most part, they cannot.

Too cool for too long and not enough heat as the others have said. Try it as in the right microclimate it might work.