Related Clues:
- Become dangerous, as roads
- Frost over
- Requiring defrosting
- Become frozen
- Make navigation difficult
- Get a winter coat?
- Put on a winter coat?
- Get slippery, in a way
- Become blocked, in a way
- Freeze, as a windshield
- Get a frosty coating
- Require salting, maybe
- Become unnavigable in winter
- Acquire a wintry glaze
- Become impassable, in a way