Dyfed Powys Police are warning that throwing snowballs at vehicles could lead to a collision.
With snow having fallen overnight and more expected, the police are reminding young people not to throw snow at vehicles.
They are also urging them to be careful around homes and when people are walking in the street.
Chief Inspector Mark Bleasdale said: "We want the young people who are lucky enough to have a day off school to enjoy the wintry weather. However, we do ask that they have respect for others and not put people in danger by throwing snowballs at vehicles."