You are colder than I am I have had one 8b winter in the last 7 years, otherwise they have been all 9a.
Although we have fairly warm winters in Seattle they tend to be very wet.

For this area the European Fan Palm is just on the treshhold of hardy. Some people lose them in our coldest years (I have), but generally that has to do with poor drainage too. I think with dry conditions it might go down to 8a, perhaps 7b with mild protection.

Needle Palm I don't grow this, and there are no issues with this palm around here, my reference books say 7b, I have heard of much lower though.

Windmill Palm, there are many palms given this common name. I would assume you are refering to trachycarpus fortunei. I have dozens of these in my garden ranging from seedlings to ones with 6 feet of trunk. My neighbor's is around 15 feet tall, it was grown from a 5 gallon about 10 years ago. These are tough palms, I have had them in pots that froze solid for 48 hours and they survived, they lost every frond though. Moisture does not seem to effect this palm.

I would recomend protection, a cage may be enough. I think there are links on this website that could provide you with some ideas. I don't like the idea of heater cables, because you lose power and there goes your palm.

Although I may need to move towards heater cables in the future. I have a Queen palm in a pot, thats getting too big to move to the garage in the winter, and way too tall to cage.

Hopefully someone in your zone will chime in

Hello guest!...I just so happen to be another palm enthusiast, right on the zone 6b/7a border, in southern Illinois! I would definitely protect your C. humilis, but I can tell you it wouldn't be a long term palm in our climate. Needle Palm's are "bulletproof," but need protection outdoor's when their young. Sabal minor's are also very cold hardy, but would require a little more attention than Needle Palm's during the coldest night's. I have experimented with R. hystrix and S. minor around here and they thrive! 😀