Good tips, and I have another one to add that may not be the most ethical from a former job standpoint. When I worked at an emergency room during the winter months, it was common for homeless people to come in complaining of chest pain to get a room. The issue with this method is that they would be taken back quicker, but wouldn't be guaranteed a night stay.

With chest pain, the medical staff will run an EKG and maybe a couple labs. However, once the results come back showing there is nothing medically wrong, the patient is then sent back out to brave the elements. Total stay time maybe 2-4 hours.

If you want a longer stay and you're able to travel to one, find the busiest hospital emergency room you can. The more people groaning in the waiting room, the better. Tell the desk clerk a really trivial complaint, such as finger pain or ear pain (the kind of complaint that makes them question who shows up to the ER at 3 am for that). These types of complaints are very low priority and will be the last to get treated. If done right, this will get at least 5-8 hours in the waiting room, which is still better than outside in the cold. Then when the sun comes up and it's warmer out, either tell the new clerk that you don't want to wait anymore, or just walk out.

This works a little better because ERs have to treat everyone that comes in wanting treatment (they seriously have people that show up for ear wax removal). As long as they think you want to be seen, they can't kick you out. And waiting hours in a heated waiting room is better than the brutal winter outside.