Guernsey Airport reopened at 1100 GMT after it was closed because of heavy overnight snow.
Flights are expected to be further delayed due to the closure of airports such as Gatwick where flights have been cancelled.
Five schools - St Andrew's, La Hougette, Le Rondin, the Forest and Blanchelande College - have closed.
The upper and central parishes are the worst affected and Guernsey Police have urged drivers to take care.
Most roads are said to be passable with care but police have warned conditions could worsen throughout the day.
Guernsey Post said there were no deliveries of mail from the UK but as much local mail was delivered as possible.
It said the UK mail would now be sent by sea and arrive in the island on Thursday.