Summer (December to February) is the best time to visit Devonport and northwest Tasmania. Days are long, the driving weather is good, and the Spirit of Tasmania runs at full frequency — though this is also when it is most popular and bookings for the overnight ferry should be made well in advance. January in particular fills up fast with families and road-trippers.
Autumn (March to May) offers some of the best weather in Tasmania: settled, warm, and far quieter than summer. The northwest landscapes are beautiful in autumn light and the ferry is easier to book.
Winter is cold and often grey on the north coast, with Bass Strait crossings occasionally rough. That said, the ferry runs year-round and the northwest — including Cradle Mountain — has a wild, dramatic quality in winter that some visitors prefer. Snow on the plateau is possible from June onwards.
Spring (September to November) is unpredictable but improving. Wildflowers appear in the highlands and crowds are still thin.