You don't need to cover it in the first place.Windmill palms can take temps down to 5°F.They can even be snowed on.If your temps are at 20-30° leave alone.

You don't need to cover it in the first place.Windmill palms can take temps down to 5°F.They can even be snowed on.If your temps are at 20-30° leave alone.

The issue is that the same night and a couple more, temps are forecast to drop to the low single digits, which can kill or badly damage a windmill.

I don't "know" that it will survive for you, but can tell you that such a dramatic temperature range has has gotta be far worse than no protection at all. After all, you are encouraging tender new growth only to have temperatures drop to arctic levels. I would just cover it without the lights or reduce the amount of insulation. Even the tiny lights get really hot. P.S., this is another lousy Winter here--COLD and WET..glad I only have one in the ground this year but lots in pots protected.

It's been my experience that windmill palms are NOT as tough as is often touted. Years ago I lost two windmills after exposure to 11 degrees and several nasty snowstorms. They were damaged the first year, and finished after a second moderately cold winter.
I then tried a Trachycarpus wagnerianus which I only protected the first two winters with pine needles around its trunk. It then grew nicely for several years with only a light mulch of pine needles to protect the roots. It got five or six feet of trunk. I thought it had become almost "bulletproof". Then came last year's cold winter with a low of five degrees. We also had repeated episodes of hard freezes with melted snow water in the crown. My big "Waggie" never even attempted to grow. ALL the windmills I was tracking in lower Cape May County were wiped out completely! They were all unprotected, or burlap wrapped in a few cases.
Sabal minor and Rhapidophyllum hystrix palms were not seriously impacted in my z7b climate. In fact my Sabal minor palms are freely reproducing. I have Palm "weed" seedlings sprouting in many places in my yard!

In our arid climate, those palms outdoors have lived through 115-120 degree temperatures for weeks on end. Of course, being in a dry, hot environment would be different, I think, than in a hot, enclosed and possibly wet environment. Best of luck! Let us know what happens.

Good news...we had a couple of days above 40 so I opened up my windmill wrapping and I was happy to see that things look good. One of the fronds looks a little damaged, but the rest look a healthy green color. I guess only time will tell... thanks everybody for your input.

Mine have seen temps in the 100s while covered lots of times with no ill effect...I'm sure it will be fine.