First, program your phone with the contact info for the Shelter Hotline operated by UPO. The phone number is (202) 399-7093 and the email is email@example.com.
The second thing you can do is tell homeless individuals you see―many hang or sleep at Metrorail stations―that they can go to a warming site (not a shelter) to eat, keep warm, and sleep overnight. The warming sites tonight are recreation centers so those who are homeless can enter at any time to stay warm. They will not be able to sleep until the centers close to the general public and transition to a warming site. Contact UPO and request transport for one or more people to a warming site or shelter; individuals will tell you which type of facility they like.
The third thing you can do is to tell others to program their phones and to look out for those who rely on the shelter system and warming sites.
Finally, you can learn more about Cold Emergencies by visiting the DHS website: Information About Cold Emergency Alerts.