I had my coconut palm outside for 2 days this week when we got into the 70s. The highest it got was 71F and the coldest it got was 42F the next day after it stopped raining.
I think it was a lot happier outside getting rain than it was inside. As long as temperatures are getting into the 60s every day, it should be pretty happy outside. I would bring it in when nights are getting in the 40s a lot because they will grow best without that.

All the plants that get brought in and out throughout the winter do significantly better than those that spend the entire winter indoors. I've never gotten a pygmy palm to survive an entire winter indoors but this winter it's been in my unheated garage when it's below 25F and outside the rest of the time and so far so good!

Good luck!
-Alex

I have one in the ground here that does pretty well. I typically just wrap a towel around them when we get a chill here. If it looks like it will be extended cold, I'll take some buckets and put them around the root zone to keep the ground a little warmer. It's gone from 3 feet to 7 feet at the top of the highest front this year.

I meant just outside during the warmest part of the day on warm sunny days.Its just too cool outside at night to leave them overnight. So far I've kept my coco between 64f-68f inside. Outside this winter its been exposed to 55f at the coolest to 71f at the warmest. However I believe near the wall it should be a little warmer due to radiated heat.

Just trying to see if I could get one to survive long term in a cold frame (minimal protection).I believe the mean temp is the key. One day soon it will get too big to stay inside and eventually would outgrow any green house I could buy. Just using my surroundings to my advantage it would be as simple as using a layer or 2 of plastic draped at an angle all the way around and to the ground to enclose a desired location like either a southern or western facing wall. Has the benefits of radiational heat from the wall, the wall itself is a good insulator even though the plastic isn't, has slight canopy, and will act a wind block on windy days. Not only could I modify it later with ease the platic should increase the temps inside especially on sunny days like a green house. It might just be crazy enough to work. If I could find a way to keep the nights a little warmer I might have a shot. Maybe a lot of rocks lol.

Heres why I think it might work. I have left this palm out just before Dec started for over a month strait with lows averaging in the low/mid 40f's, even watered several times and it didn't seem to have a problem but probably only due to the fact the highs averaged to about 74-77f. The palm looks good, appears to have slow growth still even indoors/ outdoors with the cool temps in the 60f's, holds onto fronds, no spear pull or anything. I'm assuming if there was root rot there would be visible signs by now in the fronds and over all health of the tree- no drooping yet. Around 60f for the mean temp seems to be the key. So far things look good. maybe I'm not so crazy! lol One day maybe I'll get one to trunk in the ground with some help in winter.

- US_Marine

Glad to hear it's doing well! Tropical palms are pretty good at showing stress quickly so if their were any problems you probably would have noticed it by now. It would be awesome to see a trunking coconut palm in Cali! There aren't a lot of them!
-Alex