CLIMATE

Tasmania has a cool temperate maritime climate, with surrounding seas and oceans moderating temperature extremes. Weather systems typically move across the State from the west, helped along by prevailing winds from the Southern Ocean.

Mild spring and summer seasons combine with warm and generally dry autumns to allow wine grapes to ripen slowly on the vine. This encourages maximum varietal flavour development with levels of natural acidity that give Tasmanian wines their characteristic freshness and balance.

Spring frosts and/or high humidity on some sites provide the greatest viticultural challenges.

In general, there is widespread variation in site attributes, such as vineyard slope and aspect, soil type, and meso-climate. Simply inferring that the State's southern vineyards are the industry's coolest and receive the most rainfall seldom rings true. Indeed, many of those located in the Coal River Valley outside Hobart figure among Tasmania's warmest, sunniest and driest sites.

Heat summation data for Tasmanian vineyards fall between 620 and 1360 growing degree days. The island State is Australia's largest single GI, but the figures on paper are nevertheless extraordinary.

North West Tasmania is a place of viticultural extremes. Leven Valley Vineyard (MJT 15.3°C; 701 GDD) is the district's coolest site. Broad Acres and Scott's Mill Estate (both MJT 17.5°C; 1149 GDD) are warmest.

Growing conditions in the Tamar Valley fall under the moderating influence of the river itself. Consider: Eversley Vines (MJT 17.7°C; 1065 GDD) and Evenfall (MJT 18.4°C; 1230 GDD). Coolest vs warmest sites.

North East data highlight a wide diversity of growing conditions. Apogee (MJT 17.2°C; 975 GDD) and Handpicked Baxters Road (MJT 18.3°C; 1247 GDD) are, respectively, coolest and warmest.

Vineyards regarded as East Coast sites are widely distributed from north to south, with Sterling Heights (the most northerly) and Saltwater River (the most southerly) being separated by two degrees of latitude. Little wonder the latter (MJT 16.0°C; 859 GDD) is the coolest, while Sterling Heights is the warmest (MJT 18.3°C; 1267 GDD) on the East Coast.

Vineyards in the Coal River Valley operate within a wide diversity of growing conditions. Data for those furthest north and inland suggest some continentality is at work. Six Friends (MJT 15.9°C; 786 GDD); Pooley Cooinda Vale (MJT 16.8°C; 929 GDD); SISU (MJT 16.8°C; 929 GDD) figure among the valley's coolest sites.

Richmond Park Estate and Strelley Farm Estate (both MJT 18.0°C; 1189 GDD) are among the warmest, along with Coal Valley Vineyard and Cross Rivulet Winery (both MJT 17.9°C; 1185 GDD). All four vineyards are located at the southern end of the valley.

Mount Direction Estate (MJT 16.9°C; 967 GDD) and Invercarron (MJT 16.9°C; 934 GDD) figure among the coolest sites in the Derwent Valley. Those considered to be the warmest include Government House Tasmania (MJT 17.8°C; 1165 GDD), Lowestoft (MJT 17.8°C; 1148 GDD) and Moorilla (MJT 17.8°C; 1148 GDD).

Vineyards in the Huon Valley/D'Entrecasteaux Channel experience a wide diversity of growing conditions, despite their relatively close proximity to one another. Nandroya Vineyard and Two Bud Spur (both MJT 14.8°C; 622 GDD) and Bruny Island Premium Wines (MJT 15.4°C; 747 GDD) appear to be the coolest sites south of Hobart. Tinderbox Vineyard (MJT 17.3°C; 1088 GDD) and Kettering's Trial Bay Estate (MJT 17.1°C; 1044 GDD) are warmest.

Tasmania's most northerly vineyard is warmest of all – Unavale (MJT 18.4°C; 1354 GDD) on Flinders Island, in Bass Strait. That noted, strong winds and drizzly weather during late October and November in particular can result in poor flowering and fruit-set. Slow-moving easterly weather systems that bring unwelcome gloom and rain in mid-summer can make harvest dates something of a moving feast as the season draws to a close. This is Tasmanian viticulture at its most challenging.

The State's highest monthly rainfall totals are typically recorded during winter and spring. Modest totals during the growing season often prompt growers to provide supplementary drip irrigation on vineyard sites to relieve vine stress and promote healthy, well balanced vegetative growth.

The Australian Government's Bureau of Meteorology allows access to climate and weather data.

More location-specific data can be accessed from My Climate View. The site utilises past data from the Bureau of Meteorology and the European Centre for Medium-Range Weather Forecasts. It's funded by the Australian Government.

Australia's climate is changing. According to the authors of Australia's Wine Future, average temperatures across all Australian wine regions are expected to increase by almost 3.0ºC by 2100. 

Tasmania's increase will be slightly less, but will exceed 2.0ºC. The island's wine industry will benefit somewhat from the moderating influences of the nearby Tasman Sea and Southern Ocean.

By 2041, Tasmania's smallest winegrowing district – the North West Coast – is predicted to be almost a full degree warmer during the growing season than the average now being experienced by the East Coast. North West Coast rainfall will decline from its annual average of 500mm to 442mm, barely 44mm more than the current figure for the East Coast.

The average growing season temperature on the East Coast will rise to 16.9ºC by 2100. That will bring this part of Tasmania roughly into line with present-day conditions in Robe (17.0ºC) on South Australia's Limestone Coast.

Many Tasmanian wine producers – including Freycinet, Gala Estate, Milton and Spring Vale on the East Coast – have planted Shiraz as a key measure of climate change adaptation.

Aridity – a measure of soil dryness that takes into account rainfall and evaporation – is also projected to increase in most Australian wine regions by 2100.

Declining winter rainfall will put water storages under stress across the country. Water conservation – as well as finding new water – will become increasingly critical issues for viticulturists, even at cool-climate southern latitudes like Tasmania.