Climate and Weather. Tasmania has four distinct seasons with the warmest months being December to March. The average maximum daily summer temperatures are between 17 and 23 degrees Celsius and winter daily temperatures sit between 3 and 11 degrees Celsius.Rainfall varies dramatically across the island.Hobart, with an average of 626 millimetres is Australia's second-driest capital city (after Adelaide), while on the west coast an annual average of 2,400 mm ensures the rainforest thrives.obart, with an average of 626 millimetres is Australia's second-driest capital city (after Adelaide), while on the west coast an annual average of 2,400 mm ensures the rainforest thrives.