It depends on how long it will be that cold. Is it too early to look at the hourly forecast? If it just dips down for an hour or two, I wouldn't worry. We've left ours hooked up and had no freezing inside. The only problem we had was that the water didn't want to flow first thing in the morning because there was some slush in the hose. The first bad thing to happen would be the hose freezing and bursting. That would happen before any damage to your internal plumbing as I assume you will have some heat going. If you want to be very careful, you could take the pressure off your hose or disconnect, but no need to go further than that. My opinion.
Just put 10 gallons of water in your tank and start your pump. Disconnect your hose just letting it drain on the ground. Then the next morning, turn on the water to your hose, if you get nothing, use your pump. Lay the hose in the sun for a half hour or so to thaw it.
A campground in my area displays a sign telling folks to disconnect the hose if a freeze is possible. Before a freezing event he goes around and unscrews hoses and lets them fall to the ground, then padlocks the hydrant. My kinda' guy.
sure disconnect - the danger is to the hydrant as was said by lynnmor. Just like the campgrounds, I have no freeze spigots at my house. Mine go into the house instead go below the frost line. Well I forget to disconnect the hose and the pipe burst. The hose was fine. A tiny insurance premium for a big policy!