DC has a right to shelter law when it's freezing. If the regular shelters, low barrier shelters, and overflow shelters are full then they will literally open up government buildings like libraries and rec centers. They will also provide free transportation to those shelters.

So, if you're worried about hypothermia, there are resources and alternatives to the use of McPherson Square as an encampment. Info on the resources:

https://www.streetsensemedia.org/article/find-shelter-winter-hypothermia/#.Y91fdivMJEY