I know this may be a long shot but I want a palm that can stay out all year round.
Needle palms are the most cold tolerant so that's the best place to start looking. No matter what you read, they are only reliably cold hardy in zone 7 and up. They will handle subzero temperatures when older, but cold winters in zone 7 can have subzero temperatures which is why I think that they are probably safest there.
But with protection, you can grow a ton of palms in a zone 5b (and by a ton I mean a few haha). Really it all depends on how much protection you are willing to give your palms. Most cold hardy palms are also hardy to many other things and are very tolerant of being given winter protection without ill effects. Windmill palms, Sabal minors, and European fan palms are just a few other examples of palms that are very cold tolerant. With the right protection, you will have no problem with those and even more tender plants. Check out Jim's pics. He lives in a zone 5 also and is growing a ton of incredible things.
Very funny about the tons part Alex! I agree, you can grow tons, but it is the number of palms you buy, they just happen to be all of the same 2 species. Where I will diverge, however, is I have found Sabal minor to be hardier than needles. I've killed far more needles than minors. Even if they defoliate they always seem to bounce back. Needles are done as soon as the spear pulls.
Have to agree with bradleyo. Minors are far more hardier for me. I have never lost one. I have 17 in ground. All of my needles have pulled at some point. I only have two left one of which is struggling to come back from spear pull 2 yrs ago.
I also agree with Brad and Chad. When young, needle palms are not very hardy at all. There are some nice and big ones in DC (the one I saw a pic of was definitely approaching 10 feet tall) so when they are established they become very cold tolerant. Sabal minors are great too though and I think that when they are both mature, they are close to equal in cold tolerance on the east coast (sabal minors don't do as well in a zone 7 in the Pacific northwest as in a zone 7 on the east coast).
When I first started growing my Sabal minor, it would get damage every year with protection, but now that it has been in the ground for almost 5 full summers- it really has gotten pretty hardy. I haven't seen winter damage on it in the past 2 winters (it's only been in the ground for 4 of them).
I'm in zone 5b and trust me, there are no palms that will grow up here year-round. You need to pot them and take them inside in the winter and put in a sunny window or use grow-lights. Some require heat mats as well to keep the soil warm. I have several that I do this with - also Banana trees, Pineapple, Passion Fruit, Bird of Paradise, Yucca, and Cacti. I had a needle palm and couldn't keep it alive - even taking it inside so don't believe the hype. The best ones I have is a Queen Palm, Sago Palm, Sabel Palm (S.C. state tree) and the Banana trees do well. I also have a Grapefruit tree (requires the heat pad) Trees I've lost are Coconut Palm (understandably), Washington palms, Pindo Palms (another one that is supposedly cold-hearty), Needle Palms. Starfruit & Avocado. Start off with a Pineapple plant. Just buy one and stick the crown in the dirt. Mine grew a pineapple 2 winters ago.! Good Luck!
Since you are going to have to protect it very well,
PLANT ANY PALM YOU LIKE
Protect it like any cold hardy plant
If your area it would be mulch, heat, enclosure hut