haha it depends on the UPS, but they can be VERY heavy if they are using the car batteries. I had to take them for repairs once a year or so. It isn't easy. Dry battery UPSs are fine though.
Also, one word of warning, if you are using an LCD, don't use the UPS. I learned the hard way when my old viewsonic's internal powersupply shorted. If you have a voltage meter, check the output on that thing. UPSs are often set to supply a higher than normal voltage when on backup, especially when they haven't been tuned for computer use. While a CRT monitor can easily handle a UPS that supplies twenty to forty extra volts, an LCD will not, at least in the long term.
And every UPS has its own delay when going from normal power to its battery, though a hospital UPS should be pretty good in that regards.
If a storm is coming, I'd charge it soon. I think it can take up to 8 hours or so.