Cars parked in a USD lot during break should have a valid permit.
You can purchase permits for $2/day from UPD.
If you choose to park in a USD lot without a permit, you may be fined $2/day if UPD tickets that area while you are away.
UPD asks that cars be parked as a group, along the farthest north row of the parking lot (this makes it easier if they have to remove snow).
Other parking options:
Carpool with other members of your group.
If you park on the street, be sure there are no restrictions (no parking during certain hours, not a snow route, etc.)
Meet your site leaders at USD Fleet and Travel and leave your car there. You do not need a parking permit. Note that not everyone can use this option (that would be too many cars – particularly during winter break when there are many groups traveling). However, talk to your site-leaders about this if needed.